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Dagilgan S, Dundar-Yenilmez E, Tuli A, Urunsak IF, Erdogan S. Acidosis defense mechanisms in the preimplantation stages of embryos in BALB/c strain mice. Theriogenology 2024; 217:136-142. [PMID: 38277795 DOI: 10.1016/j.theriogenology.2024.01.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Revised: 01/17/2024] [Accepted: 01/17/2024] [Indexed: 01/28/2024]
Abstract
Regulation of intracellular pH (pHi) is an important homeostatic function of cells. There are three major pHi regulatory mechanisms: the HCO3-/Cl- exchanger (AE), which alleviates alkalosis, and the Na+/H+ exchanger (NHE) and Na+,HCO3-/Cl- exchanger (NDBCE), both of which counteract acidosis. NHE activity, which is high at the germinal vesicle stage of oocyte, is inhibited during meiotic maturation, while this inhibition is abolished when the oocyte reaches the pronuclear (PN) stage of the zygote. On the other hand, we have previously found that NDBCE performs complementary regulation against acidosis during meiotic maturation. Additionally, we found that AE activity, which is a defense mechanism against alkalosis, gradually decreases during preimplantation period of embryonic development. Considering that NHE activity is inhibited during meiotic maturation and AE activity gradually decreases during embryonic development stages, we investigated whether NHE and NDBCE activities, both of which act against acidosis, functionally change from the PN zygote to the blastocyst stage of the embryo and identified these pH-regulating proteins at the molecular level in mice of the Balb/c strain. PN zygotes, two-cell (2-c), four-cell (4-c), morula and blastocyst stage embryos were obtained from 5-8-week-old, sexually mature female Balb/c mice by using the classical superovulation procedure. pHi was recorded by using the microspectrofluorometric technique on zygotes and embryos simultaneously loaded with the pH-sensitive fluorophore, 2',7'-Bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The activities of NHE and NDBCE were determined from the recovery curve of induced-acidosis in bicarbonate-free and bicarbonate-containing media, respectively. Specific inhibitors such as cariporide (1 μM), S3226 (1 and 10 μM), EIPA (1, 5, and 25 μM), and amiloride (1 mM) were used to functionally identify NHE isoforms, and the nonspecific inhibitor 4,4'-diisocyanatostilbene-2,2' disulphonic acid, disodium salt (DIDS) was used to confirm NDBCE activity. The isoforms of the pHi-regulatory proteins were also identified by molecular biology using real-time PCR. We found that NHE activity was high at all embryonic stages, and differences between stages were not significant. Functional and molecular findings indicated that isoforms of NHE 1 and 5 are present in the blastocyst, whereas isoforms of NHE 1, 3, and 4 are functional at earlier embryonic stages. Although the contribution of NDBCE activity to recovery from induced-acidosis was detected at all embryonic stages, it was significant only in the PN zygote and the 2-c embryo. This finding was confirmed by molecular analysis, which detected the expression of SLC4A8 encoding NDBCE at all embryonic stages. In conclusion, NHE is an active and important defense mechanism against acidosis and is encoded by at least two protein isoforms in all stages of the Balb/c strain of mice. NDBCE has a supportive function in all embryonic stages, especially in the PN zygote and the 2-c embryo. Preimplantation stage embryos have effective mechanisms to defend against acidosis in response to their metabolic end products (increased acid load) and the acidic environment in utero.
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Affiliation(s)
- Senay Dagilgan
- Cukurova University Faculty of Medicine, Departments of Physiology, Balcali, 01330, Adana, Turkey
| | - Ebru Dundar-Yenilmez
- Cukurova University Faculty of Medicine, Biochemistry, Balcali, 01330, Adana, Turkey
| | - Abdullah Tuli
- Cukurova University Faculty of Medicine, Biochemistry, Balcali, 01330, Adana, Turkey
| | - Ibrahim Ferhat Urunsak
- Cukurova University Faculty of Medicine, Obstetric and Gynaecology, Balcali, 01330, Adana, Turkey
| | - Seref Erdogan
- Cukurova University Faculty of Medicine, Departments of Physiology, Balcali, 01330, Adana, Turkey.
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Cao-Pham AH, Hiong KC, Boo MV, Choo CYL, Pang CZ, Wong WP, Neo ML, Chew SF, Ip YK. Molecular characterization, cellular localization, and light-enhanced expression of Beta-Na +/H + Exchanger-like in the whitish inner mantle of the giant clam, Tridacna squamosa, denote its role in light-enhanced shell formation. Gene 2019; 695:101-112. [PMID: 30763666 DOI: 10.1016/j.gene.2019.02.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2018] [Revised: 01/19/2019] [Accepted: 02/01/2019] [Indexed: 12/17/2022]
Abstract
The fluted giant clam, Tridacna squamosa, lives in symbiosis with photosynthetic zooxanthellae, and can engage in light-enhanced growth and shell formation. Light-enhanced shell formation necessitates the elimination of excess H+ from the extrapallial fluid adjacent to the shell. This study aimed to clone Na+/H+Exchanger (NHE) from the whitish inner mantle adjacent to the extrapallial fluid of T. squamosa, to determine its cellular and subcellular localization, and to evaluate the effect of light exposure on its mRNA expression level and protein abundance therein. The complete coding cDNA sequence of NHE obtained was identified as a homolog of beta NHE (βNHE-like). It consisted of 2925 bp, encoding for a polypeptide of 974 amino acids and 107.1 kDa, and was expressed predominantly in the inner mantle. There, βNHE-like was localized in the apical membrane of the seawater-facing epithelium by immunofluorescence microscopy. After exposure to light for 12 h, the seawater-facing epithelium of the inner mantle displayed consistently stronger immunostaining than that of the control exposed to 12 h of darkness. Western blotting confirmed that light exposure significantly enhanced the protein abundance of βNHE-like in the inner mantle. These results denote that some of the excess H+ generated during light-enhanced shell formation can be excreted through the light-dependent βNHE-like of the seawater-facing epithelium to minimize the impact on the whole-body pH. Importantly, the excreted H+ could dehydrate exogenous HCO3-, and facilitate the absorption of inorganic carbon through the seawater-facing epithelium dedicated for light-enhanced shell formation due to its close proximity with the shell-facing epithelium. NUCLEOTIDE SYMBOL COMBINATIONS: Pairs: R = A/G; W = A/T; Y = C/T. Triples: D = A/G/T.
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Affiliation(s)
- Anh H Cao-Pham
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Kum C Hiong
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Mel V Boo
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Celine Y L Choo
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Caryn Z Pang
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Republic of Singapore
| | - Wai P Wong
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore
| | - Mei L Neo
- St. John's Island National Marine Laboratory, National University of Singapore, 18 Kent Ridge Road, Singapore 119227, Republic of Singapore
| | - Shit F Chew
- Natural Sciences and Science Education, National Institute of Education, Nanyang Technological University, 1 Nanyang Walk, Singapore 637616, Republic of Singapore
| | - Yuen K Ip
- Department of Biological Sciences, National University of Singapore, Kent Ridge, Singapore 117543, Republic of Singapore; The Tropical Marine Science Institute, National University of Singapore, Kent Ridge, Singapore 119227, Republic of Singapore.
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Using Oral and Colon Cancer Cells for Studying the Anticancer Properties of Antimicrobial Peptides. Methods Mol Biol 2016. [PMID: 28013517 DOI: 10.1007/978-1-4939-6737-7_25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Antimicrobial peptides (AMPs) are of importance in defense mechanism of many organisms and are potential candidate for treatment of infections in animals and humans. AMPs exhibit a wide range of immunomodulatory activities related to innate immunity, wound healing, and inflammation. AMPs also serve as drug delivery vectors, antitumor agents, and mitogenic agents. Here, we describe the investigation of anticancer and cytotoxic activities of antimicrobial peptides by colorimetric MTT assay using smooth muscle, dental pulp stem cell, human colon cancer cell line (SW620), and human oral squamous carcinoma cell line (HSC4).
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Michel MC, Seifert R. Selectivity of pharmacological tools: implications for use in cell physiology. A review in the theme: Cell signaling: proteins, pathways and mechanisms. Am J Physiol Cell Physiol 2015; 308:C505-20. [PMID: 25631871 DOI: 10.1152/ajpcell.00389.2014] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 01/24/2015] [Indexed: 01/08/2023]
Abstract
Pharmacological inhibitors are frequently used to identify the receptors, receptor subtypes, and associated signaling pathways involved in physiological cell responses. Based on the effects of such inhibitors conclusions are drawn about the involvement of their assumed target or lack thereof. While such inhibitors can be useful tools for a better physiological understanding, their uncritical use can lead to incorrect conclusions. This article reviews the concept of inhibitor selectivity and its implication for cell physiology. Specifically, we discuss the implications of using inhibitor vs. activator approaches, issues of direct vs. indirect pathway modulation, implications of inverse agonism and biased signaling, and those of orthosteric vs. allosteric, competitive vs. noncompetitive, and reversible vs. irreversible inhibition. Additional problems can result from inconsistent estimates of inhibitor potency and differences in potency between cell-free systems and intact cells. These concepts are illustrated by several examples of inhibitors displaying affinity for related but distinct targets or even unrelated targets. Of note, many of the issues being addressed are also applicable to genetic inhibition strategies. The main practical conclusion following from these concepts is that investigators should be critical in the choice of inhibitor, its concentrations, and its mode of application. When this advice is adhered to, small-molecule pharmacological inhibitors can be important experimental tools in the hand of physiologists.
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Affiliation(s)
- Martin C Michel
- Department of Pharmacology, Johannes Gutenberg University, Mainz, Germany; and
| | - Roland Seifert
- Department of Pharmacology, Hannover Medical School, Hannover, Germany
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Lyall V, Phan THT, Ren Z, Mummalaneni S, Melone P, Mahavadi S, Murthy KS, DeSimone JA. Regulation of the putative TRPV1t salt taste receptor by phosphatidylinositol 4,5-bisphosphate. J Neurophysiol 2009; 103:1337-49. [PMID: 20032236 DOI: 10.1152/jn.00883.2009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Regulation of the putative amiloride and benzamil (Bz)-insensitive TRPV1t salt taste receptor by phosphatidylinositol 4,5-bisphosphate (PIP(2)) was studied by monitoring chorda tympani (CT) taste nerve responses to 0.1 M NaCl solutions containing Bz (5 x 10(-6) M; a specific ENaC blocker) and resiniferatoxin (RTX; 0-10 x 10(-6) M; a specific TRPV1 agonist) in Sprague-Dawley rats and in wildtype (WT) and TRPV1 knockout (KO) mice. In rats and WT mice, RTX elicited a biphasic effect on the NaCl + Bz CT response, increasing the CT response between 0.25 x 10(-6) and 1 x 10(-6) M. At concentrations >1 x 10(-6) M, RTX inhibited the CT response. An increase in PIP(2) by topical lingual application of U73122 (a phospholipase C blocker) or diC8-PIP(2) (a short chain synthetic PIP(2)) inhibited the control NaCl + Bz CT response and decreased its sensitivity to RTX. A decrease in PIP(2) by topical lingual application of phenylarsine oxide (a phosphoinositide 4 kinase blocker) enhanced the control NaCl + Bz CT response, increased its sensitivity to RTX stimulation, and inhibited the desensitization of the CT response at RTX concentrations >1 x 10(-6) M. The ENaC-dependent NaCl CT responses were not altered by changes in PIP(2). An increase in PIP(2) enhanced CT responses to sweet (0.3 M sucrose) and bitter (0.01 M quinine) stimuli. RTX produced the same increase in the Bz-insensitive Na(+) response when present in salt solutions containing 0.1 M NaCl + Bz, 0.1 M monosodium glutamate + Bz, 0.1 M NaCl + Bz + 0.005 M SC45647, or 0.1 M NaCl + Bz + 0.01 M quinine. No effect of RTX was observed on CT responses in WT mice and rats in the presence of the TRPV1 blocker N-(3-methoxyphenyl)-4-chlorocinnamide (1 x 10(-6) M) or in TRPV1 KO mice. We conclude that PIP(2) is a common intracellular effector for sweet, bitter, umami, and TRPV1t-dependent salt taste, although in the last case, PIP(2) seems to directly regulate the taste receptor protein itself, i.e., the TRPV1 ion channel or its taste receptor variant, TRPV1t.
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Affiliation(s)
- Vijay Lyall
- Dept. of Physiology and Biophysics, Virginia Commonwealth Univ., Molecular Medical Research Bldg. 5052, 1220 East Broad St., Richmond, VA 23298, USA.
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Peretich AL, Abbott LL, Andrews FM, Dhar MS. Age-dependent regulation of sodium-potassium adenosinetriphosphatase and sodium-hydrogen exchanger mRNAs in equine nonglandular mucosa. Am J Vet Res 2009; 70:1124-8. [DOI: 10.2460/ajvr.70.9.1124] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Adams JM, Bardgett ME, Stocker SD. Ventral lamina terminalis mediates enhanced cardiovascular responses of rostral ventrolateral medulla neurons during increased dietary salt. Hypertension 2009; 54:308-14. [PMID: 19506102 DOI: 10.1161/hypertensionaha.108.127803] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Increased dietary salt enhances sympathoexcitatory and sympathoinhibitory responses evoked from the rostral ventrolateral medulla (RVLM). The purpose of the present study was to determine whether neurons of the forebrain lamina terminalis (LT) mediated these changes in the RVLM. Male Sprague-Dawley rats with and without LT lesions were fed normal chow and given access to water or 0.9% NaCl for 14 to 15 days. Unilateral injection of l-glutamate into the RVLM produced significantly larger increases in renal sympathetic nerve activity and arterial blood pressure of sham rats ingesting 0.9% NaCl versus water. However, these differences were not observed between ventral LT-lesioned rats drinking 0.9% NaCl versus water. Similar findings were observed when angiotensin II or gamma-aminobutyric acid was injected into the RVLM. Interestingly, a subset of animals drinking 0.9% but with damage restricted to the organum vasculosum of the lamina terminalis did not show enhanced responses to l-glutamate or gamma-aminobutyric acid. In marked contrast, RVLM injection of l-glutamate or gamma-aminobutyric acid produced exaggerated sympathetic nerve activity and arterial blood pressure responses in animals drinking 0.9% NaCl versus water after an acute ventral LT lesion or chronic lesion of the subfornical organ. Additional experiments demonstrated that plasma sodium concentration and osmolality were increased at night in rats ingesting 0.9% NaCl. These findings suggest that neurons of the ventral LT mediate the ability of increased dietary salt to enhance the responsiveness of RVLM sympathetic neurons.
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Affiliation(s)
- Julye M Adams
- Department of Physiology, University of Kentucky, 800 Rose St MS-508, Lexington, KY 40536-0298, USA
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Nicola PA, Taylor CJ, Wang S, Barrand MA, Hladky SB. Transport activities involved in intracellular pH recovery following acid and alkali challenges in rat brain microvascular endothelial cells. Pflugers Arch 2008; 456:801-12. [PMID: 18214525 DOI: 10.1007/s00424-007-0441-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Accepted: 12/22/2007] [Indexed: 11/25/2022]
Abstract
Transport activities involved in intracellular pH (pH(i)) recovery after acid or alkali challenge were investigated in cultured rat brain microvascular endothelial cells by monitoring pH(i) using a pH-sensitive dye. Following relatively small acid loads with pH(i) approximately 6.5, HCO(-)(3) influx accounted for most of the acid extrusion from the cell with both Cl(-)-independent and Cl(-)-dependent, Na(+)-dependent transporters involved. The Cl(-)-independent component has the same properties as the NBC-like transporter previously shown to account for most of the acid extrusion near the resting pH(i). Following large acid loads with pH(i) < 6.5, most of the acid extrusion was mediated by Na(+)/H(+) exchange, the rate of which was steeply dependent on pH(i). Concanamycin A, an inhibitor of V-type ATPase, had no effect on the rates of acid extrusion. Following an alkali challenge, the major component of the acid loading leading to recovery of pH(i) occurred by Cl(-)/HCO(-)(3) exchange. This exchange had the same properties as the AE-like transporter previously identified as a major acid loader near resting pH(i). These acid-loading and acid-extruding transport mechanisms together with the Na(+), K(+), ATPase may be sufficient to account not only for pH(i) regulation in brain endothelial cells but also for the net secretion of HCO(-)(3) across the blood-brain barrier.
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Affiliation(s)
- Pieris A Nicola
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1PD, UK
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JOHNSON DW, BREW BK, PORONNIK P, COOK DI, GYÖRY AZ, FIELD MJ, POLLOCK CA. Transport characteristics of human proximal tubule cells in primary culture. Nephrology (Carlton) 2007. [DOI: 10.1111/j.1440-1797.1997.tb00213.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Okada Y, Taniguchi T, Morishima S, Suzuki F, Akagi Y, Muramatsu I. Characteristics of acid extrusion from Chinese hamster ovary cells expressing different prostaglandin EP receptors. Life Sci 2006; 78:2454-62. [PMID: 16300797 DOI: 10.1016/j.lfs.2005.10.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Accepted: 10/03/2005] [Indexed: 11/29/2022]
Abstract
Acid extrusion responses to prostaglandin E2 were investigated in Chinese hamster ovary (CHO) cells heterologously expressing human EP1, EP2, and EP3I receptors (hEP1, hEP2 and hEP3I) by using a microphysiometer that detected small pH changes in the extracellular microenvironment. In the cells expressing hEP1, which is known to increase intracellular Ca2+, prostaglandin E2 (1 and 10 nM) slowly accelerated acid extrusion, but at higher concentrations an initial transient phase (approximately 5 times greater than the basal acidification) overlapped the slowly developing phase. In contrast, the cells expressing hEP2, which evokes cAMP production, showed dual responses to prostaglandin E2: an initial reduction followed by an acceleration of acid extrusion. In the cells expressing hEP3I, which is known to produce both a decrease in cAMP and a modest increase in intracellular Ca2+, acid extrusion was gradually accelerated by prostaglandin E2 and reached a plateau at around 2 min. Elimination of extracellular Ca2+ diminished the responses to prostaglandin E2 in hEP1 cells, but had little effect on the responses in hEP2 and hEP3I cells. Forskolin mimicked the dual effects of prostaglandin E2 observed in the hEP2 cells. Pretreatment with pertussis toxin inhibited the response to prostaglandin E2 in hEP3I cells, but the responses in hEP1 and hEP2 cells were not affected. Na+/H+ exchanger (NHE) inhibitors (EIPA and HOE642) suppressed all the responses induced by prostaglandin E2 in hEP1, hEP2, and hEP3I cells. These results suggest that EP receptor subtypes regulate acid extrusion mainly via NHE-1 through distinct signal transduction pathways in CHO cells.
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Affiliation(s)
- Yuichi Okada
- Division of Pharmacology, Department of Biochemistry and Bioinformative Sciences, School of Medicine, University of Fukui, Matsuoka, Fukui, 910-1193, Japan
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Di Nicolantonio R, Koutsis K, Westcott KT, Wlodek ME. Relative contribution of the prenatal versus postnatal period on development of hypertension and growth rate of the spontaneously hypertensive rat. Clin Exp Pharmacol Physiol 2006; 33:9-16. [PMID: 16445693 DOI: 10.1111/j.1440-1681.2006.04317.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
1. To determine the relative roles of the prenatal and postnatal (preweaning) environment on the development of blood pressure and growth rate in the spontaneously hypertensive rat (SHR) of the Okamoto strain, we used combined embryo transfer and cross-fostering techniques between SHR and normotensive Wistar-Kyoto (WKY) rats to produce offspring whose development was examined during the first 20 weeks of life. 2. We measured litter sizes, bodyweights and tail-cuff blood pressures in offspring at 4, 8, 12 and 20 weeks of age. We also recorded heart, kidney and adrenal weights at 20 weeks of age, when the study concluded. 3. We found that both the in utero and postnatal environments provided by the SHR mother could significantly affect WKY rat offspring growth rates, but blood pressure was unaffected in this strain. In SHR offspring, the SHR maternal in utero and suckling period both contributed to the rate of blood pressure development in the SHR, but not the final blood pressure of offspring at 20 weeks of age. This effect was greater for male than female offspring. Organ weights were largely unaffected by the perinatal environment in either strain. 4. We conclude that although the SHR maternal in utero and immediate postnatal environment both contribute to the rate of blood pressure development in the SHR, they do not appear to contribute to the final blood pressure of offspring at maturity. The SHR maternal environment also alters growth rate that may, in turn, underlie these effects on SHR blood pressure development, particularly in males.
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Kaloyianni M, Stamatiou R, Dailianis S. Zinc and 17beta-estradiol induce modifications in Na+/H+ exchanger and pyruvate kinase activity through protein kinase C in isolated mantle/gonad cells of Mytilus galloprovincialis. Comp Biochem Physiol C Toxicol Pharmacol 2005; 141:257-66. [PMID: 16054875 DOI: 10.1016/j.cca.2005.07.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/07/2005] [Revised: 06/29/2005] [Accepted: 07/04/2005] [Indexed: 10/25/2022]
Abstract
We investigated the transduction pathway mediated by Zn and 17beta-estradiol in isolated mantle/gonad cells of the mussel Mytilus galloprovincialis. Both the essential metal Zn, and the estrogen 17beta-estradiol, caused an increase in intracellular pH (pHi) of isolated mantle/gonad cells of the mussel M. galloprovincialis, thus indicating the activation of the Na+/H+ exchanger (NHE). The observed effect was inhibited by EIPA (20 nM), a specific NHE inhibitor, thus verifying NHE activation. Protein kinase C (PKC) also seemed to play an activating role in zinc and 17beta-estradiol effects on NHE and PK activity. In addition, the glycolytic enzyme pyruvate kinase (PK) was increased after zinc, while it was decreased after 17beta-estradiol treatment. It is noteworthy that, both the latter effects were reversed in the presence of EIPA, indicating the involvement of NHE in the signaling mechanism. cAMP seems to participate in the signaling mechanism induced by Zn but not to that induced by 17beta-estradiol. The potential implication of the heavy metal and 17beta-estradiol on the reproductive activity of the marine animals is discussed.
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Affiliation(s)
- Martha Kaloyianni
- Laboratory of Animal Physiology, Zoology Department, School of Biology, Faculty of Science, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
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Nilssen LS, Dajani O, Christoffersen T, Sandnes D. Sustained diacylglycerol accumulation resulting from prolonged G protein-coupled receptor agonist-induced phosphoinositide breakdown in hepatocytes. J Cell Biochem 2005; 94:389-402. [PMID: 15526278 DOI: 10.1002/jcb.20260] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Studies in various cells have led to the idea that agonist-stimulated diacylglycerol (DAG) generation results from an early, transient phospholipase C (PLC)-catalyzed phosphoinositide breakdown, while a more sustained elevation of DAG originates from phosphatidylcholine (PC). We have examined this issue further, using cultured rat hepatocytes, and report here that various G protein-coupled receptor (GPCR) agonists, including vasopressin (VP), angiotensin II (Ang.II), prostaglandin F2alpha, and norepinephrine (NE), may give rise to a prolonged phosphoinositide hydrolysis. Preincubation of hepatocytes with 1-butanol to prevent conversion of phosphatidic acid (PA) did not affect the agonist-induced DAG accumulation, suggesting that phospholipase D-mediated breakdown of PC was not involved. In contrast, the GPCR agonists induced phosphoinositide turnover, assessed by accumulation of inositol phosphates, that was sustained for up to 18 h, even under conditions where PLC was partially desensitized. Pretreatment of hepatocytes with wortmannin, to inhibit synthesis of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate (PIP2), prevented agonist-induced inositol phosphate and DAG accumulation. Upon VP stimulation the level of PIP) declined, but only transiently, while increases in inositol 1,4,5-trisphosphate (InsP3) and DAG mass were sustained, suggesting that efficient resynthesis of PIP2 allowed sustained PLC activity. This was confirmed when cells were pretreated with wortmannin to prevent resynthesis of PIP2. Furthermore, metabolism of InsP3 was rapid, compared to that of DAG, with a more than 20-fold difference in half-life. Thus, rapid metabolism of InsP3 and efficient resynthesis of PIP2 may account for the larger amount of DAG generated and the more sustained time course, compared to InsP3. The results suggest that DAG accumulation that is sustained for many hours in response to VP, Ang.II, NE, and prostaglandin F2alpha in hepatocytes is mainly due to phosphoinositide breakdown.
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Affiliation(s)
- Laila Sortvik Nilssen
- Department of Pharmacology, Medical Faculty, University of Oslo, PO Box 1057 Blindern, N-0316 Oslo, Norway.
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Preest MR, Gonzalez RJ, Wilson RW. A pharmacological examination of Na+ and Cl- transport in two species of freshwater fish. Physiol Biochem Zool 2005; 78:259-72. [PMID: 15778945 DOI: 10.1086/427058] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/13/2004] [Indexed: 11/03/2022]
Abstract
We examined branchial Na(+) and Cl(-) uptake in two species of stenohaline, freshwater fish (goldfish and the Amazonian neon tetra). Kinetic analysis revealed that the two species had similar uptake capacities and affinities for Na(+) and Cl(-). However, while uptakes of Na(+) and Cl(-) (JNain and JClin, respectively) by goldfish were completely inhibited at pH 4.5 and below, uptake in tetras was unaffected by pH down to 3.25. Examination of Cl(-) transport with blockers indicated that goldfish and neon tetras utilize Cl(-)/HCO-3 exchange; SITS and SCN(-) inhibited Cl(-) uptake in both species. In contrast, large differences in Na(+) transport were indicated between the species. In goldfish, exposure to four Na(+)/H(+) exchange blockers, as well as the Na(+) channel blocker phenamil, strongly inhibited JNain. Further, Na(+) and Cl(-) uptake were strongly inhibited by the Na(+)/K(+)/Cl(-) cotransport inhibitor furosemide, as was JNain in "Cl(-)-free" water and JClin in "Na(+)-free" water. This suggests the presence of multiple transporters and possibly even a direct linkage between the transport of Na(+) and Cl(-) in goldfish. In contrast, none of these drugs strongly reduced Na(+) transport in neon tetras, which raises the possibility of a significantly different Na(+) transport mechanism in this acid-tolerant species.
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Affiliation(s)
- Marion R Preest
- Department of Biology, University of Miami, Coral Gables, FL 33157, USA.
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Sakai H, Shirai T, Yamamoto M, Chiba Y, Misawa M. Involvement of M3 Muscarinic Receptors in ACh-Induced Increase in Membrane-Associated RhoA of Rat Bronchial Smooth Muscle. Biol Pharm Bull 2005; 28:625-8. [PMID: 15802799 DOI: 10.1248/bpb.28.625] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is known that RhoA is translocated from cytoplasm to cell membrane in bronchial smooth muscle when activated by acetylcholine (ACh) stimulation. In the present study, the effects of selective muscarinic receptor antagonist methoctramine, AF-DX116 (for M(2)) and 4-diphenylacetoxy N-methylpiperidine (4-DAMP; for M(3)) on the ACh-induced rat bronchial smooth muscle contraction and increase in membrane-associated RhoA were investigated to elucidate the muscarinic receptor subtype participating in these responses. To evaluate ACh-induced contraction of bronchial smooth muscle, bronchial ring of rat was prepared, suspended in an organ bath and the tension was measured isometrically. To quantify the ACh-induced increase in membrane-associated RhoA protein, western blot analysis was performed by using homogenates of membrane and cytosolic fractions of the rat bronchi. The muscarinic M(2) and M(3) receptors were detected by using RT-PCR in rat bronchial smooth muscle. Both the ACh-induced smooth muscle contraction and increase in membrane-associated RhoA were markedly inhibited by 4-DAMP, but not by methoctramine or AF-DX116. In conclusion, these results indicated contraction for the first time that the activation of RhoA occurs via M(3) receptor in rat bronchial smooth muscle.
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Affiliation(s)
- Hiroyasu Sakai
- Department of Pharmacology, School of Pharmacy, Hoshi University, Tokyo, Japan.
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16
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Minami N, Mori N, Nagasaka M, Harada T, Kurosawa H, Kanazawa M, Kohzuki M. Effect of high-salt diet or chronic captopril treatment on exercise capacity in normotensive rats. Clin Exp Pharmacol Physiol 2004; 31:197-201. [PMID: 15053813 DOI: 10.1111/j.1440-1681.2004.03980.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. We investigated whether chronic suppression of the renin-angiotensin system, which is known to be associated with reductions in microvascular density and vasodilator responsiveness of skeletal muscle, could affect exercise capacity in normotensive rats. 2. Rats were placed on normal rat chow, normal rat chow with captopril (100 mg/kg per day) or a high-salt diet (HS; 4%) for 4 weeks. Following these interventions, rats with indwelling carotid artery catheters were submitted to stepwise increasing exercise on a motor treadmill at a speed of 10, 20 and 30 m/min for 4 min while blood lactate was measured. 3. Blood lactate after exercise at a speed of 20 m/min was significantly higher and the duration during which rats were able to run at a speed of 30 m/min was significantly shorter in captopril-treated rats and rats fed an HS diet compared with control rats. 4. We conclude that chronic treatment with captopril or HS diet could reduce the exercise capacity in inactive normotensive rats, probably through chronic inhibition of the renin-angiotensin system.
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Affiliation(s)
- Naoyoshi Minami
- Department of Internal Medicine and Rehabilitation Science, Tohoku University Graduate School of Medicine, Sendai, Japan.
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17
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Dailianis S, Kaloyianni M. Cadmium induces both pyruvate kinase and Na+/H+exchanger activity through protein kinase C mediated signal transduction, in isolated digestive gland cells ofMytilus galloprovincialis(L.). J Exp Biol 2004; 207:1665-74. [PMID: 15073199 DOI: 10.1242/jeb.00925] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYThe present study investigates the transduction pathway mediated by cadmium in isolated digestive gland cells of mussel Mytilus galloprovincialis. The effects of cadmium treatment on a key glycolytic enzyme, pyruvate kinase (PK), and on Na+/H+ exchanger activity were examined. Cadmium (50 μmol l–1) caused a significant elevation of intracellular pH (pHi) and a rise (176%) of Na influx relative to control values. The amiloride analogue, EIPA (20 nmol l–1), a Na+/H+ exchanger blocker,together with cadmium, significantly reduced the effect of treatment by cadmium alone on both Na+ influx and pHi. In addition, PK activity was significantly increased after treatment with cadmium. PK activity was inhibited after treatment of cells with amiloride or EIPA together with cadmium. Moreover, phorbol-ester (PMA), a potent activator of protein kinase C(PKC), caused a significant rise in both pHi and PK activity, while staurosporine or calphostin C reversed both events. Adrenaline, isoprenaline and phenylephrine alone or together with cadmium also significantly increased the pHi and PK activity of isolated digestive gland cells. The latter effectors in combination with cadmium showed a synergistic effect on pHi and PK. These responses seem to be blocked by propranolol, metoprolol and prazosin. Our findings suggest a hormone-like effect of cadmium on digestive gland cells. The signal transduction pathway induced by cadmium involves the stimulation of PK, PKC and Na+/H+ exchanger in isolated digestive gland cells of Mytilus galloprovincialis.
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Affiliation(s)
- Stefanos Dailianis
- Laboratory of Animal Physiology, Zoology Department, School of Biology, Faculty of Science, Aristotle University of Thessaloniki 54124, Greece
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18
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Okada Y, Taniguchi T, Akagi Y, Muramatsu I. Two-phase response of acid extrusion triggered by purinoceptor in Chinese hamster ovary cells. Eur J Pharmacol 2002; 455:19-25. [PMID: 12433590 DOI: 10.1016/s0014-2999(02)02556-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The functional characteristics of purinoceptors in Chinese hamster ovary (CHO) cells were investigated using a microphysiometer which detects small metabolic changes to living cells in real-time as variations of pH in the extracellular microenvironment. Uridine 5'-triphosphate (UTP) increased the extracellular acidification rate biphasically, namely a transient and a steady response were observed. The transient phase reached a peak (four- to fivefold the basal extracellular acidification rate in amplitude) within 20 s and was followed by the steady phase which was sustained for more than 1 min at an amplitude less than twofold the basal extracellular acidification rate. Both phases showed a concentration-dependent increase in response to UTP. However, there was a significant difference in the pEC(50) value for UTP between the transient (4.8) and steady phases (6.1). Like UTP, ATP increased the extracellular acidification rate, but alpha,beta-methyleneATP (alpha,beta-MeATP), 2-methylthioATP (2-MeSATP), ADP, UDP and adenosine did not. This result suggests that the acid is extruded through a P2Y(2) or P2Y(2)-like purinoceptor. 5-(N-ethyl-N-isopropyl) amiloride (EIPA) and 4-isopropyl-3-methylsulphonylbenzoyl-guanidine methanesulphonate (HOE642) suppressed both phases of the UTP-stimulated extracellular acidification rate response with high affinity (pIC(50): approximately 7.0). This result suggests that the Na(+)/H(+) exchanger 1 (NHE-1) predominantly mediates the UTP-induced acid extrusion response in CHO cells. Elimination of extracellular Ca(2+) or treatment with thapsigargin diminished both phases of the UTP-stimulated extracellular acidification rate. In addition, N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide hydrochloride (W-7) also abrogated the two phases. These results are consistent with the involvement of NHE-1 which is activated via Ca(2+)/calmodulin. Persistent exposure to UTP reduced both extracellular acidification rate phases, causing desensitization of the P2Y purinoceptor. This desensitization did not affect the acid extrusion response mediated by the alpha(1)-adrenoceptor.
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Affiliation(s)
- Yuichi Okada
- Department of Pharmacology, School of Medicine, Fukui Medical University, Matsuoka, Fukui 910-1193, Japan
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19
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Gresz V, Kwon TH, Vorum H, Zelles T, Kurtz I, Steward MC, Aalkjaer C, Nielsen S. Immunolocalization of electroneutral Na(+)-HCO cotransporters in human and rat salivary glands. Am J Physiol Gastrointest Liver Physiol 2002; 283:G473-80. [PMID: 12121896 DOI: 10.1152/ajpgi.00421.2001] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Patterns of salivary HCO secretion vary widely among species and among individual glands. In particular, virtually nothing is known about the molecular identity of the HCO transporters involved in human salivary secretion. We have therefore examined the distribution of several known members of the Na(+)-HCO cotransporter (NBC) family in the parotid and submandibular glands. By use of a combination of RT-PCR and immunoblotting analyses, the electroneutral cotransporters NBC3 and NBCn1 mRNA and protein expression were detected in both human and rat tissues. Immunohistochemistry demonstrated that NBC3 was present at the apical membranes of acinar and duct cells in both human and rat parotid and submandibular glands. NBCn1 was strongly expressed at the basolateral membrane of striated duct cells but not in the acinar cells in the human salivary glands, whereas little or no NBCn1 labeling was observed in the rat salivary glands. The presence of NBCn1 at the basolateral membrane of human striated duct cells suggests that it may contribute to ductal HCO secretion. In contrast, the expression of NBC3 at the apical membranes of acinar and duct cells in both human and rat salivary glands indicates a possible role of this isoform in HCO salvage under resting conditions.
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Affiliation(s)
- V Gresz
- The Water and Salt Research Center, University of Aarhus, Denmark
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20
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Lucioni A, Womack C, Musch MW, Rocha FL, Bookstein C, Chang EB. Metabolic acidosis in rats increases intestinal NHE2 and NHE3 expression and function. Am J Physiol Gastrointest Liver Physiol 2002; 283:G51-6. [PMID: 12065291 DOI: 10.1152/ajpgi.00529.2001] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Chronic metabolic acidosis increases intestinal Na absorption, although through undefined mechanisms. Whether this occurs through enhanced expression and/or function of the brush-border Na+/H+ exchangers (NHE)2 and NHE3 is unknown. Metabolic acidosis was induced in rats by feeding ammonium chloride through their drinking water. Intestinal NHE activities were measured using brush-border 22Na+ uptake. Western and Northern blots measured changes in protein and mRNA expression, respectively. Acidosis occurred within 2 days of ammonium chloride feedings but increased after 6 days. NHE2 and NHE3 activities, protein expression, and mRNA levels increased in acidotic rats compared with controls. In contrast, basolateral NHE1 expression was not affected. Brush-border alkaline phosphatase showed no effect of metabolic acidosis on cellular differentiation. This study demonstrated a direct effect of metabolic acidosis on NHE2 and NHE3 activity, expression, and gene transcription. Metabolic acidosis is one of the few circumstances shown to affect NHE2 function and expression, thus providing insights into the role of NHE2 on intestinal physiology.
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Affiliation(s)
- Alvaro Lucioni
- Martin Boyer Laboratories, Inflammatory Bowel Disease Research Center, Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA
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21
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Shim JO, Shin CY, Lee TS, Yang SJ, An JY, Song HJ, Kim TH, Huh IH, Sohn UD. Signal transduction mechanism via adenosine A1 receptor in the cat esophageal smooth muscle cells. Cell Signal 2002; 14:365-72. [PMID: 11858944 DOI: 10.1016/s0898-6568(01)00270-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We investigated what adenosine receptor type exists and the signaling pathways on the contraction of circular muscle cells isolated by enzymatic digestion from the cat esophagus. Adenosine or the selective A1 receptor agonist R-PIA causes a concentration-dependent contraction. After pretreatment with A1 receptor antagonist, DPCPX, adenosine-mediated contraction was abolished. Adenosine-induced contraction was significantly increased when A1 receptors were preserved by pretreatment with DPCPX followed by inactivation of all unprotected receptors with N-ethylmaleimide. Adenosine- or R-PIA-induced contraction was significantly augmented in the preserved cells and the increase was abolished in the presence of the A1 receptor antagonist DPCPX. PTX abolished contraction induced by adenosine or R-PIA, implying that contraction activated by A1 receptor was coupled to a pertussis toxin (PTX)-sensitive G(i) protein. After permeabilization, contraction was inhibited by G(i2), but not by G(i1) and G(i3), antibodies. These data suggest that adenosine-induced contraction of esophagus depends on PTX-sensitive G(i2.) Adenosine- or R-PIA-induced contraction of esophageal smooth muscle cells was not affected by the phospholipase D (PLD) inhibitor rho-chloromercuribenzoic acid (rhoCMB), phospholipase A(2) (PLA(2)) inhibitor DEDA or PKC antagonist chelerythrine, but was significantly abolished by phospholipase C (PLC) inhibitor, neomycin. PLC-beta3 antibody inhibited R-PIA-induced contraction. R-PIA-induced contraction of esophageal muscle cells was inhibited by IP(3) receptor antagonist heparin, which suggests that the contraction of esophageal smooth muscle cells is dependent on phosphatidylinositol-specific phospholipase (PI-PLC) and IP(3). In conclusion, adenosine- and R-PIA-induced contraction in cat esophageal smooth muscle cell was mediated by A1 receptor. A1 receptor is coupled to PTX-sensitive G protein G(i2), which results in the activation of PI-PLC-beta3. PI hydrolysis by PI-PLC forms IP(3), which binds to IP(3) receptor on endoplasmic reticulum, resulting in the release of intracellular Ca(2+).
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MESH Headings
- Adenosine/analogs & derivatives
- Adenosine/pharmacology
- Animals
- Calcium Channels
- Cats
- Cells, Cultured
- Dose-Response Relationship, Drug
- Esophagus/cytology
- Esophagus/metabolism
- Esophagus/physiology
- GTP-Binding Protein alpha Subunit, Gi2
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Heparin/pharmacology
- Inositol 1,4,5-Trisphosphate Receptors
- Isoenzymes/metabolism
- Muscle Contraction/drug effects
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Muscle, Smooth/physiology
- Pertussis Toxin
- Phospholipase C beta
- Phospholipases/metabolism
- Proto-Oncogene Proteins/metabolism
- Purinergic P1 Receptor Agonists
- Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors
- Receptors, Purinergic P1/metabolism
- Signal Transduction/drug effects
- Type C Phospholipases/metabolism
- Virulence Factors, Bordetella/pharmacology
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Affiliation(s)
- Jun O Shim
- Department of Pharmacology, College of Pharmacy, Chung Ang University, 156-756, Seoul, South Korea
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22
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Clark SS, Perman SM, Sahin MB, Jenkins GJ, Elegbede JA. Antileukemia activity of perillyl alcohol (POH): uncoupling apoptosis from G0/G1 arrest suggests that the primary effect of POH on Bcr/Abl-transformed cells is to induce growth arrest. Leukemia 2002; 16:213-22. [PMID: 11840288 DOI: 10.1038/sj.leu.2402369] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2001] [Accepted: 10/18/2001] [Indexed: 11/09/2022]
Abstract
In hematopoietic cells, the Bcr/Abl tyrosine kinase that is encoded by the Philadelphia chromosome translocation both stimulates proliferation and activates an anti-apoptotic program that is associated with a G2/M delay upon exposure to various apoptotic stimuli. We recently reported that the monocyclic monoterpene, perillyl alcohol (POH) selectively induces in Bcr/Abl transformed cells, G0/G1 arrest and apoptosis. Therefore, POH activates anti-proliferative and apoptotic pathways against which the Bcr/Abl kinase does not protect. In this report, we show that in Bcr/Abl-transformed cells, POH induces cytoplasmic acidification, redistribution of phosphatidylserine in the plasma membrane along with DNA fragmentation, all of which can be prevented by the phorbol ester, TPA. The ability of TPA to protect against POH-induced cytotoxicity was blocked by inhibitors of protein kinase C (PKC) and the Na(+)/H(+) antiport. In contrast, TPA does not protect the cells from POH-mediated G0/G1 arrest. While POH inhibits a distal step in the mevalonate biosynthesis pathway, lovastatin, also a potential anticancer agent, inhibits the initial step in this pathway. Not surprisingly, lovastatin also induces G0/G1 arrest and apoptosis in Bcr/Abl-transformed cells, however, TPA protects cells from both apoptosis and G0/G1 arrest caused by lovastatin. Thus, in Bcr/Abl-transformed cells, POH and lovastatin cause growth arrest by different mechanisms. Together, these observations demonstrate that POH-mediated cell cycle arrest precedes apoptosis and raises the possibility that that the primary effect of POH is to induce G0/G1 arrest with apoptosis being a consequence of the growth arrest.
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Affiliation(s)
- S S Clark
- Department of Human Oncology, Oncology and the UW Comprehensive Cancer Center, University of Wisconsin, Madison, WI, USA
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23
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Jeon SH, Cho MH, Cho JH. Effects of cadmium on gap junctional intercellular communication in WB-F344 rat liver epithelial cells. Hum Exp Toxicol 2001; 20:577-83. [PMID: 11926612 DOI: 10.1191/096032701718620855] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Cadmium has been associated with a number of tumors but its role in tumor promotion has not been elucidated clearly or the results obtained from various studies have been conflicting. This study was designed to investigate the effects of cadmium on the gap junctional intercellular communication (GJIC), number of gap junctions per cell, and cell proliferation in WB-F344 rat liver epithelial cells from the viewpoint of tumor promotion. GJIC was monitored by counting the cells stained with Lucifer yellow CH dye, using the scrape-loading and dye-transfer method. The numbers of gap junctions per cell were visually quantitated after an indirect immunostaining for gap junction protein using an antibody to connexin 43. Cell proliferation was assayed by direct counting of the living cells using the trypan blue dye exclusion method. In the time course study, cells treated with 200 microM CdCl2 showed rapid and nearly complete inhibition of GJIC (approximately 14% of the control) and a decrease in the number of gap junctions per cell (approximately 21% of the control) at 30 min, and the decrease continued up to 4 h without any changes in the cell viability. Treatment with CdCl2 (7.4-200 microM) for 4 h resulted in the decrease of GJIC and gap junction numbers per cell in a dose-response pattern without changes in the cell viability. In the long-term (14 days) exposure studies at doses of 0.01-7.4 microM CdCl2, an increase in cell proliferation was observed at low doses of 0.03-2.5 microM CdCl2, with GJIC also decreasing. These data demonstrate that cadmium inhibits GJIC, reduces the number of gap junctions per cell, and induces cell proliferation while decreasing the function of the gap junction.
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Affiliation(s)
- S H Jeon
- National Veterinary Research and Quarantine Service, Anyang, South Korea
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24
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Beck JS, Coulson HF, Dove N, Kealey T. Evidence for sodium-coupled acid-base transport across the basolateral membrane of the reabsorptive duct of the human eccrine sweat gland. J Invest Dermatol 2001; 117:877-9. [PMID: 11676826 DOI: 10.1046/j.0022-202x.2001.01483.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Intracellular pH was measured in isolated nonperfused ducts of human eccrine sweat glands in vitro to investigate basolateral acid-base transport mechanisms. Bath sodium removal led to a bicarbonate-independent, 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid insensitive acidification. The recovery of this acidification was ethylisopropyl amiloride sensitive, suggestive of basolateral sodium:hydrogen exchange. Whereas bath chloride removal led to a small acidification this was not 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid sensitive and its causes remain unclear. Elevation of bath potassium to depolarize the basolateral membrane led to a small alkalinization but this was not mimicked by addition of barium or chloride removal. As chloride removal and barium addition would be expected to cause larger depolarizations than potassium elevation these observations do not support a major role for electrogenic acid-base transport. In conclusion, although this study does not support a major role for electrogenic acid-base transport, it has demonstrated the basolateral presence of sodium-coupled acid-base transport in the reabsorptive duct of the human eccrine sweat gland, which most likely represents a sodium:hydrogen exchanger involved in regulation of intracellular pH.
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Affiliation(s)
- J S Beck
- Unilever Research, Port Sunlight Laboratory, Bebington, Wirral, UK.
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25
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Abstract
The functional expression of membrane transport proteins that are responsible for exchanging sodium and protons is a ubiquitous phenomenon. Among vertebrates the Na+/H+ antiporter occurs in plasma membranes of polarized epithelial cells and non-polarized cells such as red blood cells, muscle cells, and neurons, and in each cell type the transporter exchanges one sodium for one hydrogen ion, is inhibited by amiloride, and regulates intracellular pH and sodium concentration within tight limitations. In polarized epithelial cells this transporter occurs in two isoforms, each of which is restricted to either the brush border or basolateral cell membrane, and perform somewhat different tasks in the two locations. In prokaryotic cells, sodium/proton exchange occurs by an electrogenic 1Na+/2H+ antiporter that is coupled to a primary active proton pump and together these two proteins are capable of tightly regulating the intracellular concentrations of these cations in cells that may occur in environments of 4 M NaCl or pH 10-12. Invertebrate epithelial cells from the gills, gut, and kidney also exhibit electrogenic sodium/proton exchange, but in this instance the transport stoichiometry is 2Na+/1H+. As with vertebrate electroneutral Na+/H+ exchange, the invertebrate transporter is inhibited by amiloride, but because of the occurrence of two external monovalent cation binding sites, divalent cations are able to replace external sodium and also be transported by this system. As a result, both calcium and divalent heavy metals, such as zinc and cadmium, are transported across epithelial brush border membranes in these animals and subsequently undergo a variety of biological activities once accumulated within these cells. Absorbed epithelial calcium in the crustacean hepatopancreas may participate in organismic calcium balance during the molt cycle and accumulated heavy metals may undergo complexation reactions with intracellular anions as a detoxification mechanism. Therefore, while the basic process of sodium/proton exchange may occur in invertebrate cells, the presence of the electrogenic 2Na+/1H+ antiporter in these cells allows them to perform a wide array of functions without the need to develop and express additional specialized transport proteins. J. Exp. Zool. 289:232-244, 2001.
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Affiliation(s)
- G A Ahearn
- Department of Zoology, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA.
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26
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Rajendran VM, Geibel J, Binder HJ. Characterization of apical membrane Cl-dependent Na/H exchange in crypt cells of rat distal colon. Am J Physiol Gastrointest Liver Physiol 2001; 280:G400-5. [PMID: 11171622 DOI: 10.1152/ajpgi.2001.280.3.g400] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A novel Cl-dependent Na/H exchange (Cl-NHE) has been identified in apical membranes of crypt cells of rat distal colon. The presence of Cl is required for both outward proton gradient-driven Na uptake in apical membrane vesicles (AMV) and Na-dependent intracellular pH recovery from an acid load in the crypt gland. The present study establishes that Cl-dependent outward proton gradient-driven (22)Na uptake 1) is saturated with increasing extravesicular Na concentration with a Michaelis constant (K(m)) for Na of approximately 24.2 mM; 2) is saturated with increasing outward H concentration gradient with a hyperbolic curve and a K(m) for H of approximately 1.5 microM; 3) is inhibited by the Na/H exchange (NHE) inhibitors amiloride, ethylisopropylamiloride, and HOE-694 with an inhibitory constant (K(i)) of approximately 480.2, 1.1, and 9.5 microM, respectively; 4) is inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, an anion exchange inhibitor at low concentration and a Cl channel blocker at high dose, and by 5-nitro-2(3-phenylpropylamino)benzoic acid, a Cl channel blocker, with a K(i) of approximately 280.6 and 18.3 microM, respectively; and 5) substantially stimulated Cl-NHE activity by dietary Na depletion, which increases plasma aldosterone and inhibits NHE in surface cell AMV. These properties of Cl-NHE are distinct from those of NHE1, NHE2, and NHE3 isoforms that are present in colonic epithelial cells; thus these results suggest that the colonic crypt cell Cl-NHE is a novel NHE isoform.
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Affiliation(s)
- V M Rajendran
- Department of Internal Medicine, Yale University, New Haven, Connecticut 06520, USA
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27
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Murthy KS, Makhlouf GM. Heterologous desensitization mediated by G protein-specific binding to caveolin. J Biol Chem 2000; 275:30211-9. [PMID: 10862762 DOI: 10.1074/jbc.m002194200] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
We examined the notion that sequestration of G protein subunits by binding to caveolin impedes G protein reassociation and leads to transient, G protein-specific desensitization of response in dispersed smooth muscle cells. Cholecystokinin octapeptide (CCK-8) and substance P (SP) were used to activate G(q/11), cyclopentyl adenosine (CPA) was used to activate G(i3), and acetylcholine (ACh) was used to activate both G(q/11) and G(i3) via m3 and m2 receptors, respectively. CCK-8 and SP increased only Galpha(q/11), and CPA increased only Galpha(i3) in caveolin immunoprecipitates; caveolin and other G proteins were not increased. ACh increased both Galpha(q/11) and Galpha(i3) in a time- and concentration-dependent fashion: only Galpha(q/11) was increased in the presence of an m2 antagonist, and only Galpha(i3) was increased in the presence of an m3 antagonist. To determine whether transient G protein binding to caveolin affected subsequent responses mediated by the same G protein, PLC-beta activity was measured in cells stimulated sequentially with two different agonists that activate either the same or a different G protein. After treatment of the cells with ACh and an m2 antagonist, the phospholipase C-beta (PLC-beta) response to CCK-8 and SP, but not CPA, was decreased; conversely, after treatment of the cells with ACh and an m3 antagonist, the PLC-beta response to CPA, but not CCK-8 or SP, was decreased. Similarly, after treatment with CCK-8 or SP, the PLC-beta response mediated by G(q/11) only was decreased, whereas after treatment with CPA, the PLC-beta response mediated by G(i3) only was decreased. A caveolin-binding Galpha(q/11) fragment blocked the binding of activated Galpha(q/11) but not Galpha(i3) to caveolin-3 and prevented desensitization of the PLC-beta response mediated only by other G(q/11)-coupled receptors. A caveolin-binding Galpha(i3) fragment had the reverse effect. Thus, transient binding of receptor-activated G protein subunits to caveolin impedes reassociation of the heterotrimeric species and leads to desensitization of response mediated by other receptors coupled to the same G protein.
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Affiliation(s)
- K S Murthy
- Departments of Physiology and Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond, Virginia 23298-0711, USA.
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28
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THE MECHANISM OF CONTRACTION BY 2-CHLOROADENOSINE IN CAT DETRUSOR MUSCLE CELLS. J Urol 2000. [DOI: 10.1097/00005392-200002000-00067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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29
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Affiliation(s)
- L Counillon
- Laboratoire de Physiologie Cellulaire et Moléculaire, CNRS UMR 6548, 33 Av. de Valombrose, 06189 Nice, France
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30
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Khan I, Ali M. Altered expression of the Na+/H+ exchanger isoform-3 in experimental colitis: effect of garlic. Mol Cell Biochem 1999; 200:77-84. [PMID: 10569186 DOI: 10.1023/a:1006990027764] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The sodium-hydrogen exchanger isoform, NHE-3 is essential for the absorption of sodium and water from intestine. Whether this protein plays any role in inflammatory bowel disease is less understood. To address this issue, NHE-3 mRNA and protein levels were estimated in the terminal ileum and colon of the rats having colitis induced with trinitrobenzenesulphonic acid (TNBS). The effect of garlic (Allium sativum) was also evaluated on the expression of NHE-3. The animals were treated with garlic extract intraperitoneally starting 2 h before the TNBS administration until day 4 post-TNBS administration and were sacrificed on day 5. In control animals, the levels of NHE-3 in colon was higher than the ileum. As a result of colitis, the levels of NHE-3 protein and mRNA increased both in the colon and terminal ileum. Garlic treatment of the colitic animals resulted in a selective suppression of NHE-3 in the terminal ileum. Colitis caused an induction of the myeloperoxidase activity, the marker of inflammation in the colon but not in the ileum. These findings suggest that induction of NHE-3 is not primarily due to inflammation. Selective suppression of this protein in ileum by garlic may cause loss of sodium chloride and water during colitis.
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Affiliation(s)
- I Khan
- Department of Biochemistry, Faculty of Medicine, Kuwait University
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Claiborne JB, Blackston CR, Choe KP, Dawson DC, Harris SP, Mackenzie LA, Morrison-Shetlar AI. A mechanism for branchial acid excretion in marine fish: identification of multiple Na+/H+ antiporter (NHE) isoforms in gills of two seawater teleosts. J Exp Biol 1999; 202:315-24. [PMID: 9882643 DOI: 10.1242/jeb.202.3.315] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Both Na+/H+ exchange and the electrogenic extrusion of H+ via an H+-ATPase have been postulated to drive acid excretion across the branchial epithelium of fishes. While the H+-ATPase/Na+ channel system appears to be the predominant mechanism in some freshwater species, it may play a reduced role in seawater and brackish-water animals, where high external Na+ concentrations may thermodynamically favor Na+/H+ exchange driven by a Na+/H+ antiporter (NHE). In this study, we used molecular and immunological methods to assess the role of NHE isoforms in the branchial epithelium of the marine long-horned sculpin (Myoxocephalus octodecimspinosus) and the euryhaline killifish (Fundulus heteroclitus).Northern blot analysis of RNA probed with the human NHE-1 BamHI fragment suggested the presence of homologous gill NHE mRNA in sculpin. RT-PCR on gill RNA isolated from sculpin recovering from metabolic acidosis provided evidence for two distinct NHE isoforms; one with 76 % amino acid homology to mammalian NHE-2, and another 92 % homologous to trout erythrocytic beta-NHE. Killifish also have transcripts with 91 % homology to beta-NHE. Immunological detection using monoclonal antibodies for mammalian NHE-1 revealed a protein antigenically similar to this isoform in the gills of both species. Metabolic acidosis caused an approximately 30-fold decrease in expression of the NHE-1-like protein in sculpin. We speculate that beta-NHE in the gills plays the intracellular ‘housekeeping’ roles described for mammalian NHE-1. During systemic acidosis, apical gill NHE-2 (which is sensitive to external amiloride and low [Na+]) in parallel with a dramatic suppression of basolateral NHE-1 activity enhances net capdelta H+ transfers to the water.
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Affiliation(s)
- J B Claiborne
- Department of Biology, Georgia Southern University, Statesboro, GA 30460, USA.
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Takaichi K, Miyajima Y, Hanai JI, Kurokawa K, Fujita T, Warnock DG. Expression of transfected human Na+/H+ exchanger (NHE-1) in the the basolateral membrane of opossum kidney cells. J Cell Physiol 1999; 178:44-50. [PMID: 9886489 DOI: 10.1002/(sici)1097-4652(199901)178:1<44::aid-jcp6>3.0.co;2-o] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Some epithelial cells have Na+/H+ exchanger (NHE) activity in both apical and basolateral membranes. Amiloride-sensitive NHE-1 is generally identified in the basolateral membrane. The renal cell line, OK7a, targets amiloride-resistant NHE predominantly to the apical membrane. It is controversial whether the transfected NHE-1 is targeted preferentially to the basolateral membrane in OK7a cells, when human NHE-1 is chronically expressed under control of constitutively active promoters. We tried to identify the membranes in which the transfected human NHE-1 could be detected following acute expression in OK7a cells. We have always observed small Na(+)-dependent pH recovery in the basolateral membrane in OK7a cells. It is, however, controversial whether or not OK7a cells express NHE activity in the basolateral membrane. We also characterized Na(+)-dependent pH recovery in the basolateral membrane. It was not inhibited by [4,4'diisothiocyanatostilbene-2,2'-disulfonic acid] (DIDS), [4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid] (SITS), or contralateral amiloride. Li+ but not K+, chol+, or NMG+ could replace Na+. These results are consistent with the presence of the NHE in the basolateral membrane. NHE activities were predominant in the apical membrane and those in both membranes were resistant to amiloride analogs. After stable transfection with human NHE-1 in a vector utilizing the metallothionein promoter, overnight induction with Zn(2+)increased the NHE activity and its sensitivity to amiloride only in the basolateral membrane in OK7a cells. We conclude that the transfected human NHE-1 is exclusively targeted to the basolateral membrane of OK7a cells during acute induction.
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Affiliation(s)
- K Takaichi
- Fourth Department of Internal Medicine, University of Tokyo School of Medicine, Japan
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Drummond HA, Price MP, Welsh MJ, Abboud FM. A molecular component of the arterial baroreceptor mechanotransducer. Neuron 1998; 21:1435-41. [PMID: 9883735 DOI: 10.1016/s0896-6273(00)80661-3] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Baroreceptor nerve endings detect acute fluctuations in arterial pressure. We tested the hypothesis that members of the DEG/ENaC family of cation channels, which are responsible for touch sensation in Caenorhabditis elegans, may be components of the baroreceptor mechanosensor. We found the gamma subunit of ENaC localized to the site of mechanotransduction in baroreceptor nerve terminals innervating the aortic arch and carotid sinus. A functional role for DEG/ENaC members was suggested by blockade of baroreceptor nerve activity and baroreflex control of blood pressure by an amiloride analog that inhibits DEG/ENaC channels. These data suggest that ENaC subunits may be components of the baroreceptor mechanotransducer and pave the way to a better definition of mechanisms responsible for blood pressure regulation and hypertension.
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Affiliation(s)
- H A Drummond
- Department of Internal Medicine, Howard Hughes Medical Institute, University of Iowa College of Medicine, Iowa City 52242, USA
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Prpic V, Fitz JG, Wang Y, Raymond JR, Garnovskaya MN, Liddle RA. Inhibition of Na+/H+ exchange stimulates CCK secretion in STC-1 cells. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:G689-95. [PMID: 9756498 DOI: 10.1152/ajpgi.1998.275.4.g689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
It has been demonstrated that K+ channel regulation of membrane potential is critical for control of CCK secretion. Because certain K+ channels are pH sensitive, it was postulated that pH affects K+ channel activity in the CCK-secreting cell line STC-1 and may participate in regulating CCK secretion. The present study examines the role of electroneutral Na+/H+ exchange on extracellular acidification and hormone secretion. Treatment of STC-1 cells with the amiloride analog ethylisopropyl amiloride (EIPA) to inhibit Na+/H+ exchange inhibited Na+-dependent H+ efflux and increased basal CCK secretion. Substituting choline for NaCl in the extracellular medium elevated basal intracellular Ca2+ concentration and stimulated CCK release. Stimulatory effects on hormone secretion were blocked by the L-type Ca2+ channel blocker diltiazem, indicating that secretion was dependent on the influx of extracellular Ca2+. To determine whether the effects of EIPA and Na+ depletion were due to membrane depolarization, we tested graded KCl concentrations. The ability of EIPA to increase CCK secretion was inhibited by depolarization induced by 10-50 mM KCl in the bath. Maneuvers to lower intracellular pH (pHi), including reducing extracellular pH (pHo) to 7.0 or treatment with sodium butyrate, significantly increased CCK secretion. To examine whether pH directly affects membrane K+ permeability, we measured outward currents carried by K+, using whole cell patch techniques. K+ current was significantly inhibited by lowering pHo to 7.0. These effects appear to be mediated through changes in pHi, because intracellular dialysis with acidic solutions nearly eliminated current activity. These results suggest that Na+/H+ exchange and membrane potential may be functionally linked, where inhibition of Na+/H+ exchange lowers pHi and depolarizes the membrane, perhaps through inhibition of pH-sensitive K+ channels. In turn, K+ channel closure and membrane depolarization open voltage-dependent Ca2+ channels, leading to an increase in cytosolic Ca2+ and CCK release. The effects of pHi on K+ channels may serve as a potent stimulus for hormone secretion, linking cell metabolism and secretory functions.
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Affiliation(s)
- V Prpic
- Department of Medicine, Duke University Medical Center, Durham 27710; and Durham Veterans Affairs Medical Center, Durham, North Carolina 27705, USA
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35
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Duerr JM, Ahearn GA. Phorbol ester activation of an NHE-like electroneutral Na+/H+ antiporter in isolated E-cells of lobster (Homarus americanus) hepatopancreas. ACTA ACUST UNITED AC 1998. [DOI: 10.1002/(sici)1097-010x(19980601)281:2<97::aid-jez4>3.0.co;2-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Barr KJ, Garrill A, Jones DH, Orlowski J, Kidder GM. Contributions of Na+/H+ exchanger isoforms to preimplantation development of the mouse. Mol Reprod Dev 1998; 50:146-53. [PMID: 9590530 DOI: 10.1002/(sici)1098-2795(199806)50:2<146::aid-mrd4>3.0.co;2-k] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Previous work provided evidence of Na+/H+ exchanger activity in the apical domain of mouse trophectodermal plasma membranes that provides a route for entry of extracellular Na+ (Manejwala et al., 1989). This activity was hypothesized to contribute to the trans-trophectodermal Na+ flux that is required for blastocoel expansion. In the present work, we have used reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry to identify members of the Na+/H+ exchanger (NHE) family that are likely to participate in this process. When cDNA preparations from ovulated oocytes and several stages of preimplantation development were tested with PCR primers specific for the NHE-1, -2, -3, and -4 isoforms of the exchanger, only amplicons representing the NHE-1 and NHE-3 isoforms were detected. The identity of these amplicons was confirmed by direct sequencing. NHE-1 mRNA is present in oocytes and in all preimplantation stages, increasing threefold on a per embryo basis between the 4-cell and blastocyst stages. NHE-3 mRNA, on the other hand, was only detected in oocytes. Immunocytochemical analysis of blastocysts revealed that NHE-1 is localized in the basolateral domain of the trophectoderm, whereas NHE-3 is localized in the apical domain, a situation like that in epithelia of adult organs. We conclude that NHE-3, an oogenetic product that persists into the blastocyst stage, is the Na+/H+ exchanger isoform most likely to be involved in blastocoel expansion.
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Affiliation(s)
- K J Barr
- Department of Physiology, The University of Western Ontario, London, Canada
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37
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Zerbini G, Mangili R, Pozza G. Independence of dimethylamiloride-sensitive Li+ efflux pathways and Na+-Li+ countertransport in human erythrocytes. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1371:129-33. [PMID: 9565666 DOI: 10.1016/s0005-2736(98)00012-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The in vivo function of the erythrocyte Na+-Li+ countertransport (SLC) is unknown. Whether SLC may reflect an operational mode of the widespread Na+-H+ exchanger (NHE) or may otherwise be expression of an independent membrane transport, remains presently unclear. We explored the presence of 5-(N,N-dimethyl)-amiloride (DMA)-sensitive Li+ pathways in human erythrocytes where the activity of the Na+ pump, Na+-K+ cotransport and anion exchange were suitably inhibited. A total of 0.02 mM DMA had no effect on SLC as expected, but gave a significant inhibition of Li+ efflux into both Na+ and Na+-free media. This DMA-sensitive Li+ pathway, but not SLC, was significantly enhanced by hyperosmolar cell shrinkage, which is a characteristic feature of NHE. In conclusion, DMA-sensitive Li+ pathways, possibly mediated by NHE, are present in erythrocytes and coexist with the DMA-insensitive, SLC. This finding supports the notion that SLC is independent of amiloride-sensitive NHE.
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Affiliation(s)
- G Zerbini
- Renal Pathophysiology Laboratory, Division of Medicine, Scientific Institute San Raffaele, University of Milan, Milan I-20132, Italy
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38
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Garnovskaya MN, Mukhin Y, Raymond JR. Rapid activation of sodium-proton exchange and extracellular signal-regulated protein kinase in fibroblasts by G protein-coupled 5-HT1A receptor involves distinct signalling cascades. Biochem J 1998; 330 ( Pt 1):489-95. [PMID: 9461547 PMCID: PMC1219164 DOI: 10.1042/bj3300489] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
These experiments tested the hypothesis that signalling elements involved in the activation of the extracellular signal-regulated protein kinase (ERK) mediate rapid activation of sodium-proton exchange (NHE) in fibroblasts when both signals are initiated by a single G protein-coupled receptor, the 5-HT1A receptor. Similarities between the two processes were comparable concentration-response curves and time-courses, and overlapping sensitivity to some pharmacological inhibitors of tyrosine kinases (staurosporine and genistein), and phosphoinositide 3'-kinase (wortmannin and LY204002). Activation of NHE was much more sensitive to the phosphatidylcholine-specific phospholipase inhibitor (D609) than was ERK. Neither pathway was sensitive to manoeuvres designed to block PKC. In contrast, Src or related kinases appear to be required to activate ERK, but not NHE. Transfection of cDNA constructs encoding inactive mutant phosphoinositide 3'-kinase, Grb2, Sos, Ras, and Raf molecules were successful in attenuating ERK, but had essentially no effect upon NHE activation. Finally, PD98059, an inhibitor of mitogen activated/extracellular signal regulated kinase kinase, blocked ERK but not NHE activation. Thus, in CHO fibroblast cells, activation by the 5-HT1A receptor of ERK and NHE share a number of overlapping features. However, our studies do not support a major role for ERK, when activated by the 5-HT1A receptor, as a short-term upstream regulator of NHE activity.
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Affiliation(s)
- M N Garnovskaya
- Department of Medicine (Nephrology Division) Medical University of South Carolina Charleston, S.C. 29425, USA
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39
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Vilella S, Zonno V, Ingrosso L, Verri T, Storelli C. Electroneutral Na+/H+ exchange in brush-border membrane vesicles from Penaeus japonicus hepatopancreas. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:R486-93. [PMID: 9486308 DOI: 10.1152/ajpregu.1998.274.2.r486] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
An electroneutral Na+/H+ exchange mechanism (dimethylamiloride inhibitable, Li+ sensitive, and Ca2+ insensitive) was identified in brush-border membrane vesicles (BBMV) from Kuruma prawn hepatopancreas by monitoring Na(+)-dependent H+ fluxes with the pH-sensitive dye acridine orange and measuring 22Na+ uptake. Kinetic parameters measured under short-circuited conditions were the Na+ concentration that yielded one-half of the maximal dissipation rate (Fmax) of the preset transmembrane delta pH (KNa) = 15 +/- 2 mM and Fmax = 3,626 +/- 197 delta F.min-1.mg protein-1, with a Hill coefficient for Na+ of approximately 1. In addition, the inhibitory constant for dimethylamiloride was found to be approximately 1 microM. The electroneutral nature of the antiporter was assessed in that an inside-negative transmembrane electrical potential neither affected kinetic parameters nor stimulated pH-dependent (intracellular pH > extracellular pH) 22Na+ uptake. In contrast, electrogenic pH-dependent 22Na+ uptake was observed in lobster hepatopancreatic BBMV. Substitution of chloride with gluconate resulted in increasing KNa and decreasing delta Fmax, which suggests a possible role of chloride in the operational mechanism of the antiporter. These results indicate that a Na+/H+ exchanger, resembling the electroneutral Na+/H+ antiporter model, is present in hepatopancreatic BBMV from the Kuruma prawn Penaeus japonicus.
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Affiliation(s)
- S Vilella
- Dipartimento di Biologia, Università di Lecce, Strada Provinciale Lecce-Monteroni, Italy
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40
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Christ MJ, Iwamoto LM, de Silva A, Lavallee SL, Nakamura KT. Amiloride-induced contraction of isolated guinea pig, mouse, and human fetal airways. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:R209-13. [PMID: 9458920 DOI: 10.1152/ajpregu.1998.274.1.r209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Nebulized amiloride has been proposed as therapy in cystic fibrosis to block Na+ hyperabsorption in airway epithelium and prevent dehydration of secretions. Patients with cystic fibrosis often have reaction airways. Bovine and canine trachea relax to amiloride in vitro, suggesting another benefit as a bronchodilator, whereas guinea pig trachea, a useful model of human airways, does not. We hypothesized that human airways would respond like guinea pig airways. Airway ring segments from guinea pigs, mice, and human fetuses were constricted with the concentration of acetylcholine producing 50-75% maximum contraction. Subsequent changes in isometric tension to cumulative additions of amiloride (10(-8)-10(-4) M) were measured. Guinea pig airways contracted 29 +/- 5%, mouse airways contracted 23 +/- 6%, and human fetal airways contracted 30 +/- 8%. Contraction to amiloride was mimicked by dimethylamiloride, a more selective inhibitor of the Na+/H+ antiporter, and was attenuated by protein kinase C (PKC) inhibition with GF109203X and staurosporine. The present study indicates that amiloride-induced airway contraction in guinea pigs and mice closely parallels the response in isolated human airways and that the mechanism may involve the Na+/H+ antiporter and PKC.
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Affiliation(s)
- M J Christ
- Department of Clinical Investigation, Tripler Army Medical Center, Honolulu 96859, USA
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41
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Kuemmerle JF, Murthy KS, Makhlouf GM. Longitudinal smooth muscle of the mammalian intestine. A model for Ca2+ signaling by cADPR. Cell Biochem Biophys 1997; 28:31-44. [PMID: 9386891 DOI: 10.1007/bf02738308] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ca2+ mobilization in muscle cells from the circular muscle layer of the mammalian intestine is mediated by IP3-dependent Ca2+ release. Ca2+ mobilization in muscle from the adjacent longitudinal muscle layer involves a distinct, phosphoinositide-independent pathway. Receptors for contractile agonists in longitudinal muscle cells are coupled via a pertussis toxin-sensitive G protein to activation of PLA2 and formation of arachidonic acid (AA). The latter activates Cl- channels resulting in depolarization of the plasma membrane and opening of voltage-sensitive Ca2+ channels. Ca2+ influx via these channels induces Ca2+ release by activating sarcoplasmic ryanodine receptor/Ca2+ channels. The increase in [Ca2+]i activates membrane-bound ADP ribosyl cyclase, and the resultant formation of cADPR enhances Ca(2+)-induced Ca2+ release.
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Affiliation(s)
- J F Kuemmerle
- Department of Physiology, Medical College of Virginia, Richmond 23298-0711, USA
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42
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43
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Kaloyianni M, Giannisis G, Gavriil P, Boukla A. Metabolic effects and cellular volume responses induced by noradrenaline in nucleated erythrocytes. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1997; 279:337-46. [PMID: 9360315 DOI: 10.1002/(sici)1097-010x(19971101)279:4<337::aid-jez3>3.0.co;2-p] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The mechanism of adrenergic swelling, cAMP accumulation and associated Na+ and K+ concentration changes was investigated in amphibian Rana ridibunda erythrocytes. The addition of noradrenaline to an isotonic suspension of red cells of frog Rana ridibunda in the presence of the phosphodiesterase inhibitor isobutyryl-methylxanthine (IBMX), induced a significant increase of the cell volume. Forskolin treatment showed analogous results. The removal of the Na+ from the incubation medium, inhibited the volume changes caused by either noradrenaline or forskolin. Under the same conditions a more than two-fold increase of lactate formation, 260% increase of glucose consumption and accumulation of cAMP were found. These effects are specific and rapid. The peak of lactate production at 7.5 min was followed by a slow further decrease, whereas cAMP reached a plateau after 15 min. The increased glycolytic rate is probably the consequence of an activation of phosphofructokinase by cAMP. When the red cells were incubated in the presence of either noradrenaline or the cAMP analog, dibutyryl-cAMP the intracellular concentration of Na+ was significantly increased by the first 7.5 min of incubation compared with the initial values. Both the adrenergic activation and dibutyryl-cAMP treatment induced an intracellular decrease in the K+ content by 15%. In the presence of amiloride the Na+ and the K+ content of erythrocytes remained unaltered. Cellular swelling may be a prerequisitive for activation of Na+ and K+ movements. These findings suggest a regulatory role of cAMP in the energy metabolism of Rana ridibunda erythrocytes. In addition, the adrenergic responses were rapid and specific to alpha 1 and beta-antagonists.
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Affiliation(s)
- M Kaloyianni
- Zoology Department, School of Biology, Aristotle University of Thessaloniki, Greece
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44
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Busche R, Bartels J, Genz AK, von Engelhardt W. Effect of SCFA on intracellular pH and intracellular pH regulation of guinea-pig caecal and colonic enterocytes and of HT29-19a monolayers. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. PART A, PHYSIOLOGY 1997; 118:395-8. [PMID: 9366078 DOI: 10.1016/s0300-9629(96)00327-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The response of the intracellular pH (pHi, measured with BCECF) of the caecal and distal colonic epithelium of guinea pig and of monolayers of HT29 clone 19a cells on the addition of short-chain fatty acids (SCFA) was assessed. Addition of SCFA to the luminal side of these cells had no major effect on pHi, independent of whether the apical Na+/H+ exchange or the apical K+/H+ ATPase was inhibited or not. Addition of SCFA to the serosal side, on the other hand, caused a marked decrease of pHi, followed by an effective regulation back to basal values, and after removal of the acid, the cells became alkalinized. Intracellular pH is mainly regulated by mechanisms in the basolateral membrane. The basolateral Na+/H+ exchanger and the Cl-/HCO3- exchanger were mainly responsible for pHi regulation. Inhibition studies are consistent with a NHE-1 type Na+/H+ exchanger in the basolateral membranes. The apical Na+/H+ exchanger of caecal enterocytes and in HT29 cells, and the apical K+/H+ ATPase in the apical membrane of the distal colon have no or little influence on pHi regulation. The comparison shows that the HT29-19a cell line is an adequate model for studying pHi phenomena of hind gut epithelial cells.
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Affiliation(s)
- R Busche
- Department of Physiology, School of Veterinary Medicine, Hannover, Germany.
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45
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Cutaia M, Dawicki DD, Papazian LM, Parks N, Clarke E, Rounds S. Differences in nucleotide effects on intracellular pH, Na+/H+ antiport activity, and ATP-binding proteins in endothelial cells. In Vitro Cell Dev Biol Anim 1997; 33:608-14. [PMID: 9338142 DOI: 10.1007/s11626-997-0110-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Bovine (BPAEC) and human (HPAEC) pulmonary artery endothelial cell monolayers were incubated with either ATP, ATP analogues, or UTP, followed by measurement of intracellular pH (pHi) and the rate of recovery from acidosis. ATP increased baseline pHi and the rate of acid recovery in BPAEC. This response was inhibited by the amiloride analogue, methyisobutylamiloride, demonstrating that activation of the Na+/H+ antiport was responsible for the increase in baseline pHi and the recovery from acidosis. This response had the features of both a P2Y and P2U purinergic receptor, based on the responses to a series of ATP analogues and UTP. In contrast, none of the nucleotides had any significant effect on pHi and Na+/H+ antiport activity in HPAEC. This difference in the response to extracellular nucleotides was not due to a difference in ATP metabolism between cell types, since the ectonucleotidase-resistant analogue. ATP gamma S, also had no effect on HPAEC. Analogues of cAMP had no effect on pHi or acid recovery in either cell type. Incubation of BPAEC and HPAEC with the photoaffinity ligand [32P] 8-AzATP indicated that both BPAEC and HPAEC possess an ATP-binding protein of 48 kDa. However, BPAEC exhibited an additional binding protein of 87 kDa. Thus, the contrasting response to extracellular ATP between bovine and human pulmonary artery endothelial cells may be related to differences in the signal transduction pathway leading to antiport activation, including different ATP-binding sites on the cell membrane.
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Affiliation(s)
- M Cutaia
- Veterans Administration Medical Center, Brown University School of Medicine, Providence, Rhode Island, USA
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46
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Abstract
1. Macula densa (MD) cells are located within the thick ascending limb (TAL) and have their apical surface in contact with tubular fluid and their basilar region in contact with the glomerulus. These cells sense changes in luminal fluid sodium chloride concentration ([NaCl]) and transmit signals resulting in changes in vascular resistance (tubuloglomerular feedback) and renin release. 2. Current efforts have focused on understanding the cellular transport mechanisms of MD cells. Progress in this area has benefited from the use of the isolated perfused TAL-glomerular preparation, which permits direct access to MD cells. 3. Using microelectrodes to measure basolateral membrane potential (VBL) of MD cells, it was found that VBL was very sensitive to changes in luminal fluid [NaCl]. As [NaCl] was elevated from 20 to 150 mmol/L, VBL was found to depolarize by over 30 mV. 4. Basolateral membrane potential measurements were also used to identify an apical Na+:2Cl-:K+ cotransport pathway in MD cells that is the major pathway for NaCl entry into these cells. 5. Other work identified a basolateral chloride channel that is presumed to be responsible for changes in VBL during alterations in luminal [NaCl]. This channel, which is the predominant conductance across the basolateral membrane, may be regulated by intracellular Ca2+ and cAMP. 6. An apical Na+:H+ exchanger in MD cells was detected by measuring changes in intracellular pH using the fluorescent probe 2',7'-bis-(2-carboxyethyl)-5(and-6) carboxyfluorescein. 7. Using patch-clamp techniques, a high density of pH- and Ca(2+)-sensitive K+ channels was observed at the apical membrane of MD cells. 8. Other studies found that, at the normal physiological conditions prevailing at the end of the TAL (luminal [NaCl] of 20-60 mmol/L), reabsorption mediated by MD cells is very sensitive to changes in luminal [NaCl].
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Affiliation(s)
- P D Bell
- Department of Medicine, University of Alabama at Birmingham 35294, USA.
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Loghman-Adham M, Rohrwasser A, Helin C, Zhang S, Terreros D, Inoue I, Lalouel JM. A conditionally immortalized cell line from murine proximal tubule. Kidney Int 1997; 52:229-39. [PMID: 9211368 DOI: 10.1038/ki.1997.325] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have developed a conditionally immortalized murine cell line with proximal tubule characteristics (tsMPT) and a background suitable for genetic manipulations. tsMPT was derived from the F1 progeny of crosses between: [1] a transgenic mouse harboring a gamma-interferon (IFN-gamma)-inducible, temperature sensitive SV40 large T antigen gene (tsA58) and [2] mice of the 129/SvEv strain, the background from which most embryonic stem (ES) cells are derived. Under permissive conditions (33 degrees C and in the presence of IFN-gamma), tsMPT cells grow rapidly as monolayers with a doubling time of 23 hours; the large T antigen can be detected by immunocytochemistry and by Western blotting. When transferred to non-permissive conditions (39 degrees C, without IFN-gamma), the cells undergo differentiation coinciding with the disappearance of the large T antigen. By electron microscopy, tsMPT cells are polarized and show microvilli at their apical surface. tsMPT cells express brush border enzymes gamma-glutamyl transpeptidase and carbonic anhydrase IV. They possess Na(+)-dependent transport systems for Pi, D-glucose and L-proline as well as an amiloride-insensitive Na(+)-H+ exchanger. Intracellular cAMP generation is stimulated by parathyroid hormone but not by arginine vasopressin. Angiotensinogen mRNA and protein are present in tsMPT with markedly higher levels at non-permissive conditions. tsMPT cells should be a useful model for investigation of the functional features of the proximal tubule epithelium in relation to cellular differentiation.
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Affiliation(s)
- M Loghman-Adham
- Howard Hughes Medical Institute, Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, USA
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Hanai JI, Takaichi K, Miyajima Y, Fujita T, Kurokawa K. Na+/H+ exchanger (NHE) in the basolateral membrane is encoded by NHE-1 mRNA in LLC-PK1 clone 4 cells. J Cell Physiol 1997; 171:318-24. [PMID: 9180901 DOI: 10.1002/(sici)1097-4652(199706)171:3<318::aid-jcp10>3.0.co;2-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Several isoforms of Na+/H+ exchanger (NHE-1-5) have been identified. LLC-PK1 clone 4 (CL4) expresses the amiloride-sensitive type of NHE predominantly in the basolateral membrane, which is believed to be NHE-1. It is not clear whether CL4 expresses NHE in the apical membrane and which side of NHE is encoded by the NHE-1 mRNA. Using acidified CL4 cells on the filter membrane, we examined Na(+)-dependent pH recovery of the apical and basolateral membranes separately. Na+ applied to the apical membrane recovered cell pH. Na(+)-dependent pH recovery in the apical membrane was not inhibited by SITS, DIDS, or contralateral amiloride. Li+ but not K+, chol+, or NMG+ could replace Na+. These data are consistent with the presence of NHE in the apical membrane. Transfection with an antisense oligonucleotide corresponding to the 5' terminal site of NHE-1 cDNA of CL4 decreased NHE activity in the basolateral membrane but not in the apical membrane. We conclude that CL4 expresses NHE activities in both apical and basolateral membranes and that NHE-1 mRNA encodes NHE only in the basolateral membrane.
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Affiliation(s)
- J I Hanai
- First Department of Internal Medicine, University of Tokyo, Japan
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Abstract
Signal transduction in gastric and intestinal smooth muscle is mediated by receptors coupled via distinct G proteins to various effector enzymes, including PI-specific PLC-beta 1 and PLC-beta 3, and phosphatidylcholine (PC)-specific PLC, PLD and PLA2. Activation of these enzymes is different in circular and longitudinal muscle cells, generating Ca(2+)-mobilizing (IP3, AA, cADPR) and other (DAG) messengers responsible for the initial and sustained phases of contraction, respectively. IP3-dependent Ca2+ release occurs only in circular muscle. Ca2+ mobilization in longitudinal muscle involves a cascade initiated by agonist-induced transient activation of PLA2 and formation of AA, AA-dependent depolarization of the plasma membrane and opening of voltage-sensitive Ca2+ channels. The influx of Ca2+ induces Ca2+ release by activating sarcoplasmic ryanodine receptor/Ca2+ channel and stimulates cADPR formation which enhances Ca(2+)-induced Ca2+ release. The initial [Ca2+]i transient in both muscle cell types results in Ca2+/calmodulin-dependent activation of MLC kinase, phosphorylation of MLC20 and interaction of actin and myosin. The sustained phase is mediated by a Ca(2+)-independent isoform of PKC, PKC-epsilon DAG for this process is generated by PLC- and PLD-mediated hydrolysis of PC. Relaxation is mediated by cAMP-and/or cGMP-dependent protein kinase which inhibit the initial [Ca2+]i transient and reduce the sensitivity of MLC kinase to [Ca2+]i. Relaxation induced by the main neurotransmitters, VIP and PACAP, involves two cascades, one of which reflects activation of adenylyl cyclase. A distinct cascade involves G-protein-dependent stimulation of Ca2+ influx leading to Ca2+/calmodulin-dependent activation of a constitutive eNOS in muscle cells; the generation of NO activates soluble guanylyl cyclase. The resultant activation of PKA and PKG is jointly responsible for muscle relaxation.
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Affiliation(s)
- G M Makhlouf
- Department of Medicine and Physiology, Medical College of Virginia, Richmond 23298-0711, USA
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Garnovskaya MN, Gettys TW, van Biesen T, Prpic V, Chuprun JK, Raymond JR. 5-HT1A receptor activates Na+/H+ exchange in CHO-K1 cells through Gialpha2 and Gialpha3. J Biol Chem 1997; 272:7770-6. [PMID: 9065439 DOI: 10.1074/jbc.272.12.7770] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
5-HT1A receptors couple to many signaling pathways in CHO-K1 cells through pertussis toxin-sensitive G proteins. The purpose of this study was to determine which members of the Gi/o/z family mediate 5-HT1A receptor-activated Na+/H+ exchange as measured by microphysiometry of cell monolayers. The method was extensively validated, showing that proton efflux was sodium-dependent, inhibited by amiloride analogs, and activated by growth factors, phorbol ester, calcium ionophore, and hypertonic stress. 5-HT and the specific agonist (+/-)-8-hydroxy-2-(di-N-propylamino)tetralin hydrobromide rapidly stimulated proton efflux that was blocked by a specific receptor antagonist, amiloride analogs or pertussis toxin. The activation by 5-HT depended upon extracellular sodium and could be demonstrated under conditions of imposed intracellular acid load, as well as in the presence and absence of glycolytic substrate. Acceleration of proton efflux was not inhibited by sequestration of G protein betagamma-subunits, a maneuver that blocked 5-HT1A receptor activation of mitogen-activated protein kinase. Transfection of Gzalpha and pertussis toxin-resistant mutants of Goalpha and Gialpha1 did not reverse the blockade induced by pertussis toxin. In contrast, pertussis toxin-resistant mutants of Gialpha2 and Gialpha3 "rescued" the ability of 5-HT to increase proton efflux after pertussis toxin treatment. These experiments demonstrate clearly that Gialpha2 and Gialpha3 can specifically mediate rapid agonist-induced acceleration of Na+/H+ exchange.
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Affiliation(s)
- M N Garnovskaya
- Department of Medicine, Medical University of South Carolina and Veterans Affairs Medical Centers, Charleston, South Carolina 29425, USA
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