51
|
Hice RE, Folander K, Salata JJ, Smith JS, Sanguinetti MC, Swanson R. Species variants of the IsK protein: differences in kinetics, voltage dependence, and La3+ block of the currents expressed in Xenopus oocytes. Pflugers Arch 1994; 426:139-45. [PMID: 8146016 DOI: 10.1007/bf00374681] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have compared the slowly activating K+ currents (IsK) resulting from the expression of the human, mouse, or rat IsK proteins in Xenopus oocytes, utilizing natural, species-dependent sequence variations to initiate structure-function studies of this channel. Differences were found between the human and rodent currents in their voltage dependence, kinetics, and sensitivity to external La3+. The current/voltage relationships of the human and rat IsK currents differed significantly, with greater depolarizations required for activation of the human channel. The first 30 s of activation during depolarizations to potentials between -10 and +40 mV was best described by a triexponential function for each of the three species variants. The activation rates were, however, significantly faster for the human current than for either of the rodent forms. Similarly, deactivation kinetics were best described as a biexponential decay for each of the species variants but the human currents deactivated more rapidly than the rodent currents. The human and the rodent forms of IsK were also differentially affected by external La3+. Low concentrations (10, 50 microM) rapidly and reversibly reduced the magnitude of the mouse and rat currents during a test depolarization and increased the deactivation rates of the tail currents. In contrast, the magnitude and deactivation rates of the human IsK currents were unaffected by 50 microM La3+.
Collapse
Affiliation(s)
- R E Hice
- Department of Pharmacology, Merck Research Laboratories, West Point, PA 19486
| | | | | | | | | | | |
Collapse
|
52
|
Parkman HP, Wang MB, Ryan JP. Decreased electromechanical activity of guinea pig circular muscle during pregnancy. Gastroenterology 1993; 105:1306-12. [PMID: 7901106 DOI: 10.1016/0016-5085(93)90133-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
BACKGROUND Delayed gastric emptying has been reported during pregnancy; however, its underlying mechanism is poorly understood. The purpose of this study was to determine if electromechanical activity of antral circular muscle is decreased during pregnancy. METHODS Antral muscle strips from third-trimester pregnant and age-matched control virgin female guinea pigs were studied in vitro. RESULTS Spontaneous and bethanechol-induced phasic antral contractions from pregnant guinea pigs were reduced significantly in force compared with control virgin animals. Although the resting membrane potentials were similar, the electric slow waves of pregnant animals displayed significant decreases in upstroke amplitude, plateau amplitude, and number of spikes during the plateau potential compared with control animals. The voltage-tension relationship was similar in pregnant and control animals. CONCLUSIONS This study indicates that (1) the force of antral circular muscle contractions is decreased during pregnancy and (2) this decreased force is secondary to a diminished slow wave depolarization. The results suggest that a change in electromechanical activity of gastric muscle is a cause of altered gastric motility in pregnancy.
Collapse
Affiliation(s)
- H P Parkman
- Department of Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania
| | | | | |
Collapse
|
53
|
Anwer K, Oberti C, Perez GJ, Perez-Reyes N, McDougall JK, Monga M, Sanborn BM, Stefani E, Toro L. Calcium-activated K+ channels as modulators of human myometrial contractile activity. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 265:C976-85. [PMID: 8238323 DOI: 10.1152/ajpcell.1993.265.4.c976] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The role of Ca(2+)-activated potassium (KCa) channels in the regulation of membrane potential, intracellular free calcium ([Ca2+]i) and contraction was investigated in uterine smooth muscle and myometrial cells. In an immortalized human myometrial cell line, oxytocin increased [Ca2+]i and [3H]inositol phosphate formation. Relaxin attenuated the oxytocin-induced increase in [Ca2+]i. In cell-attached patches, membrane depolarization activated a large-conductance KCa channel (179 +/- 4 pS). Iberiotoxin (IbTX), a potent blocker of "maxi" KCa channels (A. Galvez, G. Gimenez-Gallego, J. P. Reuben, L. Roy-Contanciin, P. Feigenbaum, G. J. Kaczorowski, and M. L. Garcia. J. Biol. Chem. 265: 11083-11090, 1990) produced long closed events (approximately 6 min) in these channels. In agreement with this blockage, IbTX depolarized the cells by 9.8 +/- 2.8 mV and caused a dose-dependent increase in [Ca2+]i with a half-maximal effective concentration of 0.79 nM. IbTX also caused phasic contractions in human myometrial strips and increased both the frequency and force of spontaneous contractions in estrogen-primed rat myometrial strips. Moreover, myometrial contractility was also affected by 1 mM tetraethylammonium, a concentration that blocks uterine smooth muscle KCa channels when applied to the extracellular side (G. J. Perez, L. Toro, S. D. Erulkar, and E. Stefani. Am. J. Obstet. Gynecol. 168: 652-660, 1993). These results strongly suggest that the large conductance KCa channels may actively participate in the control of human myometrial cell membrane potential and [Ca2+].
Collapse
Affiliation(s)
- K Anwer
- Department of Biochemistry, University of Texas Medical School at Houston
| | | | | | | | | | | | | | | | | |
Collapse
|
54
|
Fomina AF, Kostyuk PG, Sedova MB. Glucocorticoid modulation of calcium currents in growth hormone 3 cells. Neuroscience 1993; 55:721-5. [PMID: 8413934 DOI: 10.1016/0306-4522(93)90437-k] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Clonal malignant pituitary growth hormone 3 cells were used for the analysis of the influence of hydrocortisone and dexamethasone on voltage-gated calcium currents and hormone secretion. The whole-cell patch-clamp technique was used. The presence of low-threshold inactivating and high-threshold persisting components in the total calcium current was shown; they could be separated at less negative holding potential level. Some increase in current densities of both components was observed as early as 30 min after treatment with 10(-6) mol/l glucocorticoids. The increase was maximal for both types of currents after 2 h of incubation; however, the high-threshold component was affected much more strongly (current density increased by more than four-fold) than the low-threshold one (current density increased by about a three-fold). Potentiation of currents was blocked by actinomycine D (10(-4) M), suggesting that protein synthesis was required. A substantial increase in growth hormone secretion (measured by radioimmunoassay method) was observed in the same cells after 2 h of incubation with hydrocortisone, while the secretion of prolactin remained even slightly depressed.
Collapse
Affiliation(s)
- A F Fomina
- Bogomoletz Institute of Physiology, Ukrainian Academy of Sciences
| | | | | |
Collapse
|
55
|
Takimoto K, Fomina AF, Gealy R, Trimmer JS, Levitan ES. Dexamethasone rapidly induces Kv1.5 K+ channel gene transcription and expression in clonal pituitary cells. Neuron 1993; 11:359-69. [PMID: 8352944 DOI: 10.1016/0896-6273(93)90191-s] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Glucocorticoids specifically increase Kv1.5 K+ channel mRNA in normal and clonal (GH3) rat pituitary cells. Here, we demonstrate that dexamethasone, a glucocorticoid agonist, rapidly induces Kv1.5 gene transcription, but does not affect Kv1.5 mRNA turnover (t1/2 approximately 0.5 hr) in GH3 cells. Immunoblots indicate that the steroid also increases the expression of the 76 kd Kv1.5 protein approximately 3-fold within 12 hr without altering its half-life (t1/2 approximately 4 hr). In contrast, Kv1.4 protein expression is unaffected. Finally, we find that the induction of Kv1.5 protein is associated with an increase in a noninactivating component of the voltage-gated K+ current. Our results indicate that hormones and neurotransmitters may act within hours to regulate excitability by controlling K+ channel gene expression.
Collapse
Affiliation(s)
- K Takimoto
- Department of Pharmacology, University of Pittsburgh, Pennsylvania 15261
| | | | | | | | | |
Collapse
|
56
|
Swanson R, Hice RE, Folander K, Sanguinetti MC. The IsK protein, a slowly activating voltage-dependent K+ channel. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/s1044-5765(05)80006-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
57
|
Adelwoehrer NE, Mahnert W. Hexoprenaline activates potassium channels of human myometrial myocytes. Arch Gynecol Obstet 1993; 252:179-84. [PMID: 8512346 DOI: 10.1007/bf02426355] [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: 01/31/2023]
Abstract
Hexoprenaline is a beta-adrenergic agent used for tocolysis after the 26th week of pregnancy. The purpose of the present study was to demonstrate the site of action of hexoprenaline on the membrane of single isolated smooth muscle cells. The main action of beta-mimetics on the cell is hyperpolarization of the cellular membrane, i.e. beta-mimetics have similar effects as K(+)-ions (Standen et al., 1989). Our results indicate a prolonged and significantly enhanced activity of K(+)-channels in the cell membrane, as may also be demonstrated by the use of the K(+)-channel activator Calcitonin-gene related peptide (CGRP). In control experiments under physiological conditions, we observed a large conductance K(+)-channel with 158 pS. The channel was voltage dependent and Ca++ sensitive indicating that it belongs to the class of big conductance Ca(++)-activated K(+)-channels (BKCa). Hexoprenaline and CGRP both increased the open probability (P(o)) of the channel measured with the patch clamp system in the cell attached configuration. Hexoprenaline was also an activator of the BKCa in the presence of Nitrendipine, indicating that the activation of the Ca++ sensitive channel is not an indirect effect of Ca++ currents via L-type Ca++ channels.
Collapse
Affiliation(s)
- N E Adelwoehrer
- Department of Gynecology and Obstetrics, University of Graz, Austria
| | | |
Collapse
|
58
|
Dubois JM, Rouzaire-Dubois B. Role of potassium channels in mitogenesis. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1993; 59:1-21. [PMID: 8419984 DOI: 10.1016/0079-6107(93)90005-5] [Citation(s) in RCA: 116] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- J M Dubois
- Laboratoire de Physiologie cellulaire, URA CNRS 1121, Université Paris Sud, Orsay, France
| | | |
Collapse
|
59
|
Abstract
MinK is a novel protein which induces an extremely slowly activating potassium channel when expressed in Xenopus oocytes. We discuss the properties and regulation of the current and localization and possible physiological roles of the MinK protein.
Collapse
Affiliation(s)
- E M Blumenthal
- Interdepartmental Neuroscience Program, Yale University Medical School, New Haven, CT 06510
| | | |
Collapse
|
60
|
Busch AE, Kavanaugh MP, Varnum MD, Adelman JP, North RA. Regulation by second messengers of the slowly activating, voltage-dependent potassium current expressed in Xenopus oocytes. J Physiol 1992; 450:491-502. [PMID: 1432714 PMCID: PMC1176133 DOI: 10.1113/jphysiol.1992.sp019138] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
1. Voltage-clamp recordings of membrane current were made from Xenopus oocytes that had been injected with RNA which had been transcribed in vitro from a cloned complementary DNA. 2. Depolarization from -80 mV evoked outward potassium currents that developed very slowly. At -20 mV the time constant for activation was about 50 s, and at +40 mV about 6 s. 3. The potassium current was increased by the calcium ionophore A23187 or by intracellular injection of inositol 1,4,5-trisphosphate (IP3), each of which should increase the intracellular calcium concentration ([Ca2+]i). The current was decreased by injection of BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid). The current was also reduced by phorbol esters; this effect was blocked by staurosporine. 4. In oocytes that had also been injected with RNA encoding the 5-hydroxytryptamine (5-HT2) receptor, 5-HT increased the potassium current. After caffeine pretreatment, to block the release of intracellular calcium, 5-HT decreased the current; this decrease was prevented by staurosporine. 5. It is concluded that the slowly activating, voltage-dependent potassium current expressed in Xenopus oocytes is increased by increases in [Ca2+]i and is decreased by activation of protein kinase C. Stimulation of 5-HT2 receptors can have both these effects, but the former normally predominates.
Collapse
Affiliation(s)
- A E Busch
- Vollum Institute, Oregon Health Sciences University, Portland 97201
| | | | | | | | | |
Collapse
|
61
|
Phillippe M, Harrison HH. Gestational modulation of myometrial proteins in the timed-pregnant Sprague-Dawley rat. Life Sci 1992; 50:1189-200. [PMID: 1313137 DOI: 10.1016/0024-3205(92)90462-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
These studies sought to test the hypothesis that the expression of myometrial proteins is modulated as the onset of parturition approaches. Myometrial proteins from timed-pregnant rats were analyzed utilizing sodium dodecylsulfate polyacrylamide gel and 2-dimensional electrophoresis, and Western blot techniques. SDS-PAGE gels demonstrated increased expression of at least 10 protein bands from 17 to 200+ KD. 2-dimensional gels confirmed the presence of at least five groups of gestationally modulated proteins. Western blots for phosphoinositide-specific phospholipase C demonstrated significant modulation of the expression of three isozymes. These studies have confirmed differential expression of myometrial proteins near term in the timed-pregnant rat; some of which play an important role in intracellular signal transduction in response to hormones and pharmacologic agents.
Collapse
Affiliation(s)
- M Phillippe
- Department of Obstetrics and Gynecology, Pritzker School of Medicine, University of Chicago
| | | |
Collapse
|
62
|
Abstract
Patch-clamp techniques were used to investigate slowly activating, Ca(2+)-insensitive K+ channels of isolated rat olfactory receptor neurons. These channels had a unitary conductance of 135 pS and were only found in a small proportion (less than 5%) of membrane patches. Upon depolarization to voltages more positive than -50 mV, the channels activated gradually over a period of at least 10 s. When hyperpolarized to negative voltages, channel activity deactivated in a slow but voltage-dependent manner. These channels may underlie a slowly activating K+ current that is observed in approximately 30% of whole-cell recordings. Similar single channels have been reported in smooth muscle cells, but this is the first demonstration of these channels in any type of neuron. The channels may contribute to the spike frequency adaptation and post-stimulus hyperpolarization that are observed during the excitatory response to odorants. They may also contribute to cell repolarization following large odorant-stimulated receptor currents.
Collapse
Affiliation(s)
- J W Lynch
- School of Physiology and Pharmacology, University of New South Wales, Kensington, Australia
| | | |
Collapse
|
63
|
Blakely RD, Clark JA, Pacholczyk T, Amara SG. Distinct, developmentally regulated brain mRNAs direct the synthesis of neurotransmitter transporters. J Neurochem 1991; 56:860-71. [PMID: 1671586 DOI: 10.1111/j.1471-4159.1991.tb02002.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The Xenopus laevis oocyte expression system was utilized to define developmental and structural properties of neurotransmitter transporter mRNAs and the pharmacological characteristics of encoded carriers independent of the complexities of brain tissue preparations. Poly(A)+ RNA from dissected brain regions of neonatal and adult rats was microinjected into Xenopus oocytes and the expression of Na(+)-dependent neurotransmitter transporters determined 48 h later. Transport studies conducted with oocytes injected with RNAs derived from juvenile rat tissues indicate a region- and transporter-specific, postnatal increase in mRNA abundance as a major factor in the developmental changes observed for brain high-affinity amino acid uptake systems. Both L-glutamic acid (Glu) and gamma-aminobutyric acid (GABA) uptake systems were detectable by day 3 in postnatal forebrain mRNA and became progressively enriched during the next 2 weeks of forebrain development. In contrast, brainstem Glu and GABA transporter enrichment was 60-70% of adult values by day 3 and exceeded adult levels by day 10. Parallel determinations of L-glutamic acid decarboxylase mRNA abundance during development argue for distinct regulatory influences on mRNAs directing transmitter synthesis and reuptake. Glycine uptake could not be detected at any point of forebrain development and exhibited a gradual postnatal rise to adult levels over the first 3 postnatal weeks of brainstem development. Uptake studies conducted with well-characterized inhibitors of Glu, GABA, dopamine, and choline transport (D-aspartate, nipecotic acid, nomifensine, and hemicholinium-3, respectively) revealed that oocyte transporters encoded by adult rat brain mRNAs retained antagonist sensitivities exhibited by in vitro brain preparations. In addition, a differential regional sensitivity to the Glu transport antagonist dihydrokainate (1 mM) was observed, lending support to previous reports of region-specific Glu transporter subtypes. To determine the structural diversity present among brain transporter mRNAs, poly(A)+ RNA was size-fractionated on linear (10-31%) sucrose density gradients prior to oocyte injection. These experiments revealed two mRNA size classes (2.4-3.0 kb, 4.0-4.5 kb) independently capable of directing the synthesis of Glu, GABA, and glycine transporters. In regions other than the cerebellum, Glu and GABA transporter activities migrated as single, yet distinct, peaks of 4.0-4.5 kb. In contrast, both Glu and GABA transporters exhibited major peaks of activity at 2.5-3.0 kb with size-fractionated cerebellar mRNA. Brainstem glycine uptake exhibited a broad sedimentation profile, with peaks apparent at 2.4 and 4.0 kb. Taken together, these findings indicate previously unappreciated complexity in mRNA structure and regulation which underlies the expression of amino acid neurotransmitter uptake systems in the rodent CNS.
Collapse
Affiliation(s)
- R D Blakely
- Section of Molecular Neurobiology, Howard Hughes Medical Institute, New Haven, Connecticut
| | | | | | | |
Collapse
|
64
|
|
65
|
Demotes-Mainard J, Arnauld E, Vincent JD. Estrogens Modulate the Responsiveness of in vivo Recorded Striatal Neurons to lontophoretic Application of Dopamine in Rats: Role of D and D2 Receptor Activation. J Neuroendocrinol 1990; 2:825-32. [PMID: 19215425 DOI: 10.1111/j.1365-2826.1990.tb00647.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Abstract Estrogens are known to affect the functioning of the extrapyramidal motor system. Their actions concern both pre- and postsynaptic components of the dopaminergic nigrostriatal neurotransmission. Postsynaptically, estradiol alters the electrophysiological responses of striatal neurons to dopamine application. The aim of this study was to determine the respective roles of D(1) and D(2) receptor subtypes in this modification of dopamine action. Eighty-three spontaneously firing caudate neurons of ovariectomized female rats were extracellularly recorded during iontophoretic ejection of dopamine or dopaminergic agonists or antagonists. Between 5 and 10 h after a single 17beta-estradiol injection (60 mug/kg), the predominant effect of dopamine was an activation of firing (63%), and the distribution of responses significantly differed from controls and from neurons recorded less than 5 h after estradiol injection (P<0.001) on which dopamine mainly elicited inhibitory effects (71% and 63%, respectively). The excitatory effects of dopamine on this subset of spontaneously firing striatal neurons were blocked by the D(1) antagonist SCH 23390 (56%), whereas the inhibitory actions were antagonized by sulpiride (62%), whose isolated application often had an excitatory effect (54%). The distributions of the responses to specific D(1) or D(2) agonists were not altered by estrogen treatment: the predominant effect of the D(2) agonist RU 24213 was in all groups a reduction of firing rate (54%), and the D(1) agonist SKF 38393 mainly induced either a decrease in mean firing rate (21%) or a biphasic effect consisting on an excitation-inhibition sequence (53%). These results suggest that estradiol does not qualitatively alter the coupling of D(1) or D(2) receptors to their electrophysiological effectors, but rather quantitatively changes the ratio between the D(1) and D(2) receptor-mediated components of dopamine actions, reinforcing the D(1) and/or attenuating the D(2) receptor-mediated component.
Collapse
|
66
|
Schumacher M. Rapid membrane effects of steroid hormones: an emerging concept in neuroendocrinology. Trends Neurosci 1990; 13:359-62. [PMID: 1699322 DOI: 10.1016/0166-2236(90)90016-4] [Citation(s) in RCA: 231] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- M Schumacher
- Laboratory of Neuroendocrinology, Rockefeller University, New York, NY 10021
| |
Collapse
|
67
|
Sigel E. Use of Xenopus oocytes for the functional expression of plasma membrane proteins. J Membr Biol 1990; 117:201-21. [PMID: 2231695 DOI: 10.1007/bf01868451] [Citation(s) in RCA: 127] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- E Sigel
- Pharmakologisches Institut, Universität Bern, Switzerland
| |
Collapse
|
68
|
Pragnell M, Snay KJ, Trimmer JS, MacLusky NJ, Naftolin F, Kaczmarek LK, Boyle MB. Estrogen induction of a small, putative K+ channel mRNA in rat uterus. Neuron 1990; 4:807-12. [PMID: 2344412 DOI: 10.1016/0896-6273(90)90207-v] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Estrogen causes dramatic long-term changes in the activity of the uterus. Here we report the molecular cloning of a small (700 base) uterine mRNA species capable of inducing a slow K+ current in Xenopus oocytes. The 130 amino acid protein encoded by this mRNA species has a predicted structure that does not resemble that of previously described voltage-dependent channels from mammalian sources. It is, however, similar to structural motifs found in certain prokaryotic ion channels. The induction of this mRNA by estrogen is rapid; this uterine mRNA species is not detectable in uteri from estrogen-deprived rats, but is substantially induced after 3 hr of estrogen treatment. These results support a critical role for regulation of ion channel expression by estrogen in the uterus.
Collapse
Affiliation(s)
- M Pragnell
- Department of Physiology and Biophysics, University of Iowa, Iowa City 52242
| | | | | | | | | | | | | |
Collapse
|
69
|
Folander K, Smith JS, Antanavage J, Bennett C, Stein RB, Swanson R. Cloning and expression of the delayed-rectifier IsK channel from neonatal rat heart and diethylstilbestrol-primed rat uterus. Proc Natl Acad Sci U S A 1990; 87:2975-9. [PMID: 2183220 PMCID: PMC53816 DOI: 10.1073/pnas.87.8.2975] [Citation(s) in RCA: 133] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
cDNAs encoding a delayed-rectifier-type K+ channel were cloned from both neonatal rat heart and ovariectomized, diethylstilbestrol-primed rat uterus by using the polymerase chain reaction. Both clones have nucleotide sequences identical to that encoding the rat kidney IsK channel [Takumi, T., Ohkubo, H. & Nakanishi, S. (1988) Science 242, 1042-1045] and encode a putative protein of 130 amino acids. Injection of RNA transcripts of the cDNAs into Xenopus oocytes resulted in the expression of a slowly activating, voltage-dependent K+ current. An antisense oligonucleotide, derived from the sequence of the clone, specifically inhibited the expression of the slow, outward current observed in cells injected with mRNAs isolated from the parent tissues (i.e., kidney, heart, and uterus), indicating that the cloned gene underlies the major K+ current expressed from RNA isolated from these tissues.
Collapse
Affiliation(s)
- K Folander
- Department of Pharmacology, Merck Sharp & Dohme Research Laboratories, West Point, PA 19486
| | | | | | | | | | | |
Collapse
|
70
|
Sugimoto T, Tanabe Y, Shigemoto R, Iwai M, Takumi T, Ohkubo H, Nakanishi S. Immunohistochemical study of a rat membrane protein which induces a selective potassium permeation: its localization in the apical membrane portion of epithelial cells. J Membr Biol 1990; 113:39-47. [PMID: 2154581 DOI: 10.1007/bf01869604] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
We previously reported a novel rat membrane protein that exhibits a voltage-dependent potassium channel activity on the basis of molecular cloning combined with an electrophysiological assay. This protein, termed IsK protein, is small and different from the conventional potassium channel proteins but induces selective permeation of potassium ions on its expression in Xenopus oocytes. In this investigation, we examined cellular localization of rat IsK protein by preparing three different types of antibody that specifically reacts with a distinct part of rat IsK protein. Immunohistochemical analysis using these antibody preparations demonstrated that rat IsK protein is confined to the apical membrane portion of epithelial cells in the proximal tubule of the kidney, the submandibular duct and the uterine endometrium. The observed tissue distribution of rat IsK protein was consistent with that of the IsK protein mRNA determined by blot hybridization analysis. In epithelial cells, the sodium, potassium-ATPase pump in the basolateral membrane generates a sodium gradient across the epithelial cell and allows sodium ions to enter the cell through the apical membrane. Thus, taking into account the cellular localization of the IsK protein, together with its electrophysiological properties, we discussed a possible function of the IsK protein, namely that this protein is involved in potassium permeation in the apical membrane of epithelial cells through the depolarizing effect of sodium entry.
Collapse
Affiliation(s)
- T Sugimoto
- Department of Anatomy, Kansai Medical University, Osaka, Japan
| | | | | | | | | | | | | |
Collapse
|
71
|
Mathieu CL, Burnett SH, Mills SE, Overpeck JG, Bruns DE, Bruns ME. Gestational changes in calbindin-D9k in rat uterus, yolk sac, and placenta: implications for maternal-fetal calcium transport and uterine muscle function. Proc Natl Acad Sci U S A 1989; 86:3433-7. [PMID: 2717621 PMCID: PMC287147 DOI: 10.1073/pnas.86.9.3433] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Calbindin-D9k was quantified and its cellular location was defined in uterus, yolk sac, and placenta. In late gestation (days 17 to term) coordinated induction of calbindin-D9k was seen in uterine epithelial lining cells and juxtaposed yolk sac visceral epithelium as well as the intraplacental yolk sac epithelium. The induction of calbindin-D9k in these cells coincided with the time of exponential fetal bone growth and maximal fetal accumulation of calcium, suggesting a role of the protein in these epithelial layers in maternal-fetal calcium transport. Dynamic changes also occurred in the calbindin-D9k contents of the two layers of uterine smooth muscle (outer longitudinal and inner circular) during mid- and late gestation. During early pregnancy (days 0-4), calbindin-D9k was present in the two smooth muscle layers. By midgestation (day 10), calbindin-D9k had decreased by a factor of 10 in these tissue layers. During late gestation calbindin-D9k rebounded in the inner circular smooth muscle layer. These uterine changes of early and midgestation were reproduced by the endocrine changes of pseudopregnancy. Progesterone appeared to be a good candidate for controlling the midgestational decrease of uterine muscle calbindin-D9k, as it blunted estrogen's induction of the protein in the muscle layers and stroma in a dose-dependent manner. Changes in myometrial calbindin-D9k may reflect variations in muscular calcium storage, thereby representing alterations in potential for contraction.
Collapse
Affiliation(s)
- C L Mathieu
- Department of Pathology, University of Virginia School of Medicine, Charlottesville 22908
| | | | | | | | | | | |
Collapse
|
72
|
Zeitlin PL, Wagner M, Markakis D, Loughlin GM, Guggino WB. Steroid hormones: modulators of Na+ absorption and Cl- secretion in cultured tracheal epithelia. Proc Natl Acad Sci U S A 1989; 86:2502-5. [PMID: 2928347 PMCID: PMC286941 DOI: 10.1073/pnas.86.7.2502] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Cultures of tracheal epithelial cells from adult nonpregnant female rabbits maintained a different balance of Na+ absorption and Cl- secretion from cells of pregnant animals and fetal cultures. Cells of nonpregnant rabbits had a large Na+ absorptive current (11 microA/cm2 or 53% of baseline short circuit current) and a small Cl- secretory current (2.4 microA/cm2 or 11%). In contrast, fetal cells had greater Cl- secretion (15.1 microA/cm2 or 61%) and much less Na+ absorption (1.6 microA/cm2 or less than 10%). Cells of pregnant animals had amounts of Cl- secretion (11.4 microA/cm2 or 41%) and Na+ absorption (6.7 microA/cm2 or 22%) that were in between that of fetal and adult nonpregnant animals. In addition to these striking differences in baseline ion transport among the three groups, epinephrine was found to stimulate Cl- secretion in cells from pregnant rabbits, both Na+ absorption and Cl- secretion in cells from nonpregnant animals, and neither in fetal cells. Steroid hormones of pregnancy, progesterone and estradiol, when added to cells cultured from nonpregnant rabbits, altered the magnitudes of the individual transport pathways to mimic cells cultured from pregnant animals. In addition to changing baseline transport, these steroids modified the epinephrine-stimulated currents to resemble those in the fetus and in pregnancy. We conclude that steroid hormones regulate the balance of Na+ absorption and Cl- secretion in tracheal epithelia in utero and in adulthood.
Collapse
Affiliation(s)
- P L Zeitlin
- Department of Pediatrics, Johns Hopkins University, School of Medicine, Baltimore, MD 21205
| | | | | | | | | |
Collapse
|
73
|
Logan SD. Regulation of cell excitability and solute transport. Curr Opin Cell Biol 1989; 1:227-30. [PMID: 2561069 DOI: 10.1016/0955-0674(89)90092-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- S D Logan
- Department of Physiology, Medical University of Birmingham, UK
| |
Collapse
|
74
|
Affiliation(s)
- L Y Jan
- Howard Hughes Medical Institute, University of California, San Francisco 94143-0724
| | | |
Collapse
|
75
|
Expression of Mammalian Plasma Membrane Receptors in Xenopus Oocytes: Studies of Thyrotropin-Releasing Hormone Action. GENE PROBES 1989. [DOI: 10.1016/b978-0-12-185251-1.50007-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
76
|
Takumi T, Ohkubo H, Nakanishi S. Cloning of a membrane protein that induces a slow voltage-gated potassium current. Science 1988; 242:1042-5. [PMID: 3194754 DOI: 10.1126/science.3194754] [Citation(s) in RCA: 380] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A rat kidney messenger RNA that induces a slowly activating, voltage-dependent potassium current on its expression in Xenopus oocytes was identified by combining molecular cloning with an electrophysiological assay. The cloned complementary DNA encodes a novel membrane protein that consists of 130 amino acids with a single putative transmembrane domain. This protein differs from the known ion channel proteins but is involved in the induction of selective permeation of potassium ions by membrane depolarization.
Collapse
Affiliation(s)
- T Takumi
- Institute for Immunology, Kyoto University Faculty of Medicine, Japan
| | | | | |
Collapse
|