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Hepatic changes during a carrageenan induced granuloma in rats. Mediators Inflamm 2012; 2:79-83. [PMID: 18475507 PMCID: PMC2365382 DOI: 10.1155/s0962935193000110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/1992] [Accepted: 12/08/1993] [Indexed: 11/17/2022] Open
Abstract
Hepatic changes during inflammation were studied in rats bearing a carrageenan induced granuloma. In spite of a decrease in the metabolic capacity of microsomes to induce lipid peroxidation during inflammation, the endogenous lipid peroxidation remained unchanged and unrelated with the hepatic activities measured. The continuous increase in hepatic cAMP observed during acute and chronic phases could be related to adenylate cyclase stimulation by mediators, and could be an initial step in the hepatocyte adaptation leading to the increased level of hepatic caeruloplasmin, to the reduction of cytochrome P-450 level and to the modifications of Ca2+ sequestration by microsomes.
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2
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Yaekura K, Yada T. [Ca2+]i-reducing action of cAMP in rat pancreatic beta-cells: involvement of thapsigargin-sensitive stores. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:C513-21. [PMID: 9486142 DOI: 10.1152/ajpcell.1998.274.2.c513] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In the present study, we examined the ability of adenosine 3',5'-cyclic monophosphate (cAMP) to reduce elevated levels of cytosolic Ca2+ concentration ([Ca2+]i) in pancreatic beta-cells. [Ca2+]i and reduced pyridine nucleotide, NAD(P)H, were measured in rat single beta-cells by fura 2 and autofluorescence microfluorometry. Sustained [Ca2+]i elevation, induced by high KCl (25 mM) at a basal glucose concentration (2.8 mM), was substantially reduced by cAMP-increasing agents, dibutyryl cAMP (DBcAMP, 5 mM), an adenylyl cyclase activator forskolin (10 microM), and an incretin glucagon-like peptide-1-(7-36) amide (10(-9) M), as well as by glucose (16.7 mM). The [Ca2+]i-reducing effects of cAMP were greater at elevated glucose (8.3-16.7 mM) than a basal glucose (2.8 mM). An inhibitor of protein kinase A (PKA), H-89, counteracted [Ca2+]i-reducing effects of cAMP but not those of glucose. Okadaic acid, a phosphatase inhibitor, at 10-100 nM also reduced sustained [Ca2+]i elevation in a concentration-dependent manner. Glucose, but not DBcAMP, increased NAD(P)H in beta-cells. [Ca2+]i-reducing effects of cAMP were inhibited by 0.3 microM thapsigargin, an inhibitor of the endoplasmic reticulum (ER) Ca2+ pump. In contrast, [Ca2+]i-reducing effects of cAMP were not altered by ryanodine, an ER Ca(2+)-release inhibitor, Na(+)-free conditions, or diazoxide, an ATP-sensitive K+ channel opener. In conclusion, the cAMP-PKA pathway reduces [Ca2+]i elevation by sequestering Ca2+ in thapsigargin-sensitive stores. This process does not involve, but is potentiated by, activation of beta-cell metabolism. Together with the known [Ca2+]i-increasing action of cAMP, our results reveal dual regulation of beta-cell [Ca2+]i by the cAMP-signaling pathway and by a physiological incretin.
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Affiliation(s)
- K Yaekura
- Department of Physiology, Kagoshima University School of Medicine, Japan
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3
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Combettes L, Berthon B, Claret M. Caffeine inhibits cytosolic calcium oscillations induced by noradrenaline and vasopressin in rat hepatocytes. Biochem J 1994; 301 ( Pt 3):737-44. [PMID: 7519848 PMCID: PMC1137049 DOI: 10.1042/bj3010737] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effects of caffeine on agonist-induced changes in intracellular Ca2+ concentration ([Ca2+]i) were studied in single fura 2-loaded cells and suspensions of rat hepatocytes. In single cells, caffeine (5-10 mM) inhibited [Ca2+]i oscillations induced both by noradrenaline (0.1 microM) and by vasopressin (0.1 nM). Caffeine shifted the dose-response curves of the [Ca2+]i rise induced by vasopressin (0.5 to 2 nM) and noradrenaline (from 80 to 580 nM) in suspensions of liver cells loaded with quin2. This inhibitory effect of caffeine was not due to inhibition of phosphodiesterase enzymes and elevation of cyclic AMP levels, because application of 3-isobutyl-1-methylxanthine, forskolin or 8-bromo cyclic AMP had no inhibitory effect on the intracellular Ca2+ rise induced by inositol 1,4,5-trisphosphate (InsP3)-dependent agonists. We demonstrate that the inhibitory effect of caffeine may result from at least three actions of caffeine: (1) inhibition of receptor-stimulated InsP3 formation; (2) inhibition of agonist-stimulated Ca2+ influx; and (3) direct inhibition of the InsP3-sensitive Ca(2+)-release channel.
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Affiliation(s)
- L Combettes
- Unité de Recherche U274, Institut National de la Santé et de la Recherche Médicale, Université Paris Sud, Orsay, France
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4
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Bànhegyi G, Fulceri R, Bellomo G, Romani A, Pompella A, Benedetti A. Role of a nonmitochondrial Ca2+ pool in the synergistic stimulation by cyclic AMP and vasopressin of Ca2+ uptake in isolated rat hepatocytes. Arch Biochem Biophys 1991; 287:320-8. [PMID: 1654813 DOI: 10.1016/0003-9861(91)90485-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The subcellular distribution of 45Ca2+ accumulated by isolated rat hepatocytes exposed to dibutyryl cyclic AMP (dbcAMP) followed by vasopressin (Vp) was studied by means of a nondisruptive technique. When treated with dbcAMP followed by vasopressin, hepatocytes obtained from fed rats accumulated an amount of Ca2+ approximately fivefold higher than that attained under control conditions. Ca2+ released from the mitochondrial compartment by the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP) accounted for only a minor portion of the accumulated Ca2+. The largest portion was released by the Ca2+ ionophore A23187 and was attributable to a nonmitochondrial compartment. DbcAMP + Vp-treatment also caused a maximal stimulation of glucose production and a twofold increase in cellular glucose 6-phosphate levels. In hepatocytes obtained from fasted rats, dbcAMP + Vp-stimulated Ca2+ accumulation was lower, although with the same subcellular distribution, and was associated with a minimal glucose production. In the presence of gluconeogenetic substrates (lactate plus pyruvate) hepatocytes from fasted rats were comparable to cells isolated from fed animals. However, Ca2+ accumulation and glucose 6-phosphate production could be dissociated in the absence of dbcAMP, in the presence of lactate/pyruvate alone. Under this condition in fact Vp induced only a minimal accumulation of Ca2+ in hepatocytes isolated from fasted rats, although glucose production was markedly increased. Moreover, treatment of fed rat hepatocytes with 1 mM ATP caused a maximal activation of glycogenolysis, but only a moderate stimulation of cellular Ca2+ accumulation. In this case, sequestration of Ca2+ occurred mainly in the mitochondrial compartment. By contrast, the addition of ATP to dbcAMP-pretreated hepatocytes induced a large accumulation of Ca2+ in a nonmitochondrial pool. Additional experiments using the fluorescent Ca2+ indicator Fura-2 showed that dbcAMP pretreatment can enlarge and prolong the elevation of cytosolic free Ca2+ caused by Vp. A nonmitochondrial Ca2+ pool thus appears mainly responsible for the Ca2+ accumulation stimulated by dbcAMP and Vp in isolated hepatocytes, and cyclic AMP seems able to activate Ca2+ uptake in such a nonmitochondrial pool.
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Affiliation(s)
- G Bànhegyi
- Istituto di Patologia Generale, Università di Siena, Italy
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5
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Fernandez Y, Cambon-Gros C, Deltour P, Mitjavila S. Activity of liver microsomal Ca2+-ATPase in relation to perturbation of membrane hydrophobic interactions induced by methoxybenzene derivatives and n-aliphatic alcohols. Toxicol Lett 1988; 44:31-8. [PMID: 2847368 DOI: 10.1016/0378-4274(88)90126-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Changes in the activity of liver microsomal Ca2+-ATPase were studied in the presence of two series of lipophilic compounds: four flavouring substances derived from methoxybenzene and four n-aliphatic alcohols. With each compound the activity was stimulated at lower concentrations and inhibited at higher concentrations. The linear relationship between equiactive concentrations of the compounds and their partition coefficients showed that the enzyme activity was modulated by perturbation of membrane hydrophobic interactions. Measurements carried out by electron-spin resonance (ESR) showed evidence of a decrease in the membrane order induced by these compounds. However, results obtained with the methoxybenzene derivatives showed that the modification in ATPase activity cannot be directly related to the decrease in membrane order. This decrease did not only reflect perturbation of hydrophobic interactions.
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Affiliation(s)
- Y Fernandez
- U 87 INSERM, Institut de Physiologie, Toulouse, France
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6
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Romani A, Fulceri R, Pompella A, Benedetti A. MgATP-dependent, glucose 6-phosphate-stimulated liver microsomal Ca2+ accumulation: difference between rough and smooth microsomes. Arch Biochem Biophys 1988; 266:1-9. [PMID: 2972255 DOI: 10.1016/0003-9861(88)90231-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Some features of the MgATP-dependent Ca2+-accumulating capacity of rough as compared to smooth liver microsomal fraction were studied. Smooth microsomes accumulate somewhat higher amounts of Ca2+ than rough ones in the presence of MgATP. In the presence of glucose 6-phosphate, which markedly stimulates MgATP-dependent Ca2+ accumulation in both fractions, smooth microsomes exhibit a much higher Ca2+-accumulating capacity than rough ones. Possible reasons of the differences observed between the two fractions were investigated. Smooth microsomes exhibit a higher Ca2+-dependent ATPase activity, suggesting a higher Ca2+ inward transport into smooth vesicles. Also, following the inhibition of active Ca2+ transport by means of vanadate, smooth microsomes appear to release the Ca2+ previously accumulated--both in the absence (i.e., with MgATP only) and in the presence of glucose 6-phosphate--at a lower rate than rough ones. This indicates a lower passive backflux of Ca2+ accumulated in smooth vesicles. On the basis of these data, differences can be envisaged with respect to cellular Ca2+ handling by different domains of endoplasmic reticulum in the liver.
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Affiliation(s)
- A Romani
- Istituto di Patologia Generale, Università di Siena, Italy
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7
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MgATP-dependent glucose 6-phosphate-stimulated Ca2+ accumulation in liver microsomal fractions. Effects of inositol 1,4,5-trisphosphate and GTP. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)69094-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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8
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Kimura S, Robison BC, Kraus-Friedmann N. Inhibitor of anion transport, DIDS, releases Ca2+ from hepatic microsomes. Biochem Biophys Res Commun 1988; 151:396-401. [PMID: 2964822 DOI: 10.1016/0006-291x(88)90606-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Addition of 4,4'-diisothiocyanostilbene-2, 2'-disulfonic acid (DIDS) to Ca2+ loaded hepatic microsomal vesicles evoked a dose-dependent release of the accumulated Ca2+. Ca2+ uptake was also inhibited. The effects of DIDS do not seem to be due to the inhibitions of either Cl- or proton fluxes. The results indicate that DIDS inhibits Ca2+ uptake and releases Ca2+ by inhibiting the Ca2+-ATPase and the formation of the phosphorylated intermediate of the enzyme, and that it might interact with a specific site on the vesicle which is involved in the translocation of Ca2+ across the microsomal and mitochondrial membranes.
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Affiliation(s)
- S Kimura
- Department of Physiology and Cell Biology, University of Texas Health Science Center, School of Medicine, Houston 77225
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Kraus-Friedmann N, Fleschner CR, Zimniak P, Moore P. The hepatic microsomal Ca2+ sequestering system. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1988; 232:59-68. [PMID: 2975144 DOI: 10.1007/978-1-4757-0007-7_6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- N Kraus-Friedmann
- Dept. of Physiology and Cell Biology, University of Texas Medical School, Houston 77225
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Fleschner CR, Kraus-Friedmann N. Inhibition of rat liver microsomal Ca2+-ATPase by fluorescein-5'-isothiocyanate. Arch Biochem Biophys 1987; 254:448-53. [PMID: 2953307 DOI: 10.1016/0003-9861(87)90123-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Rat liver microsomal fraction was incubated at pH 8.8 with fluorescein-5'-isothiocyanate in a Tris-buffered sucrose medium. This treatment completely inhibited ATP-dependent Ca2+ transport, Ca2+-ATPase activity, and Ca2+-ATPase phosphoenzyme intermediate formation. Inhibition of Ca2+ transport and phosphoenzyme intermediate formation by fluorescein-5'-isothiocyanate was partially prevented by including ATP in the treatment medium. These data taken together are consistent with the proposal that fluorescein-5'-isothiocyanate binds the Ca2+-ATPase ATP-binding site, suggesting the presence of a lysine residue in this domain. Fluorescein-5'-isothiocyanate labeling of microsomal proteins had no measurable effect on the basal, Mg2+-ATPase activity. Using fluorescein-5'-isothiocyanate-labeled microsomal fraction, we demonstrated that the Mg2+-ATPase activity was inhibited by Ca2+.
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12
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Whipps DE, Armston AE, Pryor HJ, Halestrap AP. Effects of glucagon and Ca2+ on the metabolism of phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate in isolated rat hepatocytes and plasma membranes. Biochem J 1987; 241:835-45. [PMID: 3036077 PMCID: PMC1147637 DOI: 10.1042/bj2410835] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Rat hepatocytes whose phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) had been labelled for 60 min with 32P were treated with glucagon for 10 min or phenylephrine for 2 min. Glucagon caused a 20% increase in PIP but no change in PIP2 whereas phenylephrine caused a similar increase in PIP but a 15% decrease in PIP2. Addition of both hormones together for 10 min produced a 40% increase in PIP. A crude liver mitochondrial fraction incubated with [32P]Pi and ADP incorporated label into PIP, PIP2 and phosphatidic acid. The PIP2 was shown to be in contaminating plasma membranes and PIP in both lysosomal and plasma-membrane contamination. A minor but definitely mitochondrial phospholipid, more polar than PIP2, was shown to be labelled with 32P both in vitro and in hepatocytes. The rate of 32P incorporation into PIP was faster in mitochondrial/plasma-membrane preparations from rats treated with glucagon or if 3 microM-Ca2+ and Ruthenium Red were present in the incubation buffer. Loss of 32P from membranes labelled in vitro was shown to be accompanied by formation of inositol 1,4,5-trisphosphate (IP3) and inositol 1,4-bisphosphate, and was faster in preparations from glucagon-treated rats or in the presence of 3 microM-Ca2+. It is concluded that glucagon stimulates both PIP2 phosphodiesterase and phosphatidylinositol kinase activities, as does the presence of 3 microM-Ca2+. The resulting formation of IP3 may be responsible for the observed release of intracellular Ca2+ stores. The roles of a guanine nucleotide regulatory protein and phosphorylation in mediating these effects are discussed.
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13
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Thiyagarajah P, Lim SC. The (Ca2+ + Mg2+)-stimulated ATPase of the rat parotid endoplasmic reticulum. Biochem J 1986; 235:491-8. [PMID: 2943271 PMCID: PMC1146712 DOI: 10.1042/bj2350491] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
A membrane fraction enriched in endoplasmic reticulum was prepared from rat parotid glands by using sucrose-gradient centrifugation. The fraction showed a 10-fold increase in specific activity of NADPH: cytochrome c reductase activity over that of tissue homogenates and minimal contamination with plasma membranes or mitochondria. The endoplasmic reticulum fraction possessed both Mg2+ -stimulated ATPase as well as Ca2+, Mg2+-ATPase [( Ca2+ + Mg2+)-stimulated ATPase]activity. The Ca2+, Mg2+-ATPase required 2-5 mM-Mg2+ for optimal activity and was stimulated by submicromolar concentrations of free Ca2+. The Km for free Ca2+ was 0.55 microM and the average Vmax. was 60 nmol/min per mg of protein. The Km for ATP was 0.11 mM. Other nucleotides, such as GTP, CTP or ADP, could not substitute for ATP in supporting the Ca2+-activated nucleotidase activity. Increasing the K+ concentration from 0 to 100 mM caused a 2-fold activation of the Ca2+, Mg2+-ATPase. Trifluoperazine, W7 [N-(6-aminohexyl)-5-chloronaphthalene-1-sulphonamide] and vanadate inhibited the enzyme. The concentration of trifluoperazine and vanadate required for 50% inhibition of the ATPase were 52 microM and 28 microM respectively. Calmodulin, cyclic AMP, cyclic AMP-dependent protein kinase and inositol 1,4,5-trisphosphate had no effect on the ATPase. The properties of the Ca2+, Mg2+ -ATPase were distinct from those of the Mg2+-ATPase, but comparable with those reported for the parotid endoplasmic-reticulum Ca2+-transport system [Kanagasuntheram & Teo (1982) Biochem. J. 208, 789-794]. The results suggest that the Ca2+, Mg2+-ATPase is responsible for driving the ATP-dependent Ca2+ accumulation by this membrane.
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Fleschner CR, Kraus-Friedmann N. The effect of Mg2+ on hepatic microsomal Ca2+ and Sr2+ transport. EUROPEAN JOURNAL OF BIOCHEMISTRY 1986; 154:313-20. [PMID: 2935394 DOI: 10.1111/j.1432-1033.1986.tb09399.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The ATP-dependent uptake of Ca2+ by rat liver microsomal fraction is dependent upon Mg2+. Studies of the Mg2+ requirement of the underlying microsomal Ca2+-ATPase have been hampered by the presence of a large basal Mg2+-ATPase activity. We have examined the effect of various Mg2+ concentrations on Mg2+-ATPase activity, Ca2+ uptake, Ca2+-ATPase activity and microsomal phosphoprotein formation. Both Mg2+-ATPase activity and Ca2+ uptake were markedly stimulated by increasing Mg2+ concentration. However, the Ca2+-ATPase activity, measured concomitantly with Ca2+ uptake, was apparently unaffected by changes in the Mg2+ concentration. In order to examine the apparent paradox of Mg2+ stimulation of Ca2+ uptake but not of Ca2+-ATPase activity, we examined the formation of the Ca2+-ATPase phosphoenzyme intermediate and formation of a Mg2+-dependent phosphoprotein, which we have proposed to be an attribute of the Mg2+-ATPase activity. We found that Ca2+ apparently inhibited formation of the Mg2+-dependent phosphoprotein both in the absence and presence of exogenous Mg2+. This suggests that Ca2+ may inhibit (at least partially) the Mg2+-ATPase activity. However, inclusion of the Ca2+ inhibition of Mg2+-ATPase activity in the calculation of Ca2+-ATPase activity reveals that this effect is insufficient to totally account for the stimulation of Ca2+ uptake by Mg2+. This suggests that Mg2+, in addition to stimulation of Ca2+-ATPase activity, may have a direct stimulatory effect on Ca2+ uptake in an as yet undefined fashion. In an effort to further examine the effect of Mg2+ on the microsomal Ca2+ transport system of rat liver, the interaction of this system with Sr2+ was examined. Sr2+ was sequestered into an A23187-releasable space in an ATP-dependent manner by rat liver microsomal fraction. The uptake of Sr2+ was similar to that of Ca2+ in terms of both rate and extent. A Sr2+-dependent ATPase activity was associated with the Sr2+ uptake. Sr2+ promoted formation of a phosphoprotein which was hydroxylamine-labile and base-labile. This phosphoprotein was indistinguishable from the Ca2+-dependent ATPase phosphoenzyme intermediate. Sr2+ uptake was markedly stimulated by exogenous Mg2+, but the Sr2+-dependent ATPase activity was unaffected by increasing Mg2+ concentrations. Sr2+ uptake and Sr2+-dependent ATPase activity were concomitantly inhibited by sodium vanadate. In contrast to Ca2+, Sr2+ had no effect on Mg2+-dependent phosphoprotein formation. Taken together, these data indicate that Mg2+ stimulated Ca2+ and Sr2+ transport by increasing the Ca2+ (Sr2+)/ATP ratio.(ABSTRACT TRUNCATED AT 400 WORDS)
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15
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Chan KM, Koepnick SL. The mechanism of calcium uptake by liver microsomes: effect of anions and ionophores. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 818:291-8. [PMID: 2994726 DOI: 10.1016/0005-2736(85)90002-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The mechanism of calcium uptake by liver microsomes was investigated using various anions and ionophores. Calcium uptake was shown to be specific to microsomes and unlikely to be due to contamination by plasma membranes by correlation of calcium uptake to the marker enzymes specific for these two fractions. Under the conditions employed, phosphates, sulfate, chloride, acetate, nitrate, thiocyanate, maleate, succinate and oxalate all stimulated calcium uptake by microsomes, but to different degrees. The greatest effect (4-6-fold) was observed with phosphate. On the contrary, phosphate is the only anion that stimulates the plasma membrane calcium uptake to any significant degree. Treatment of isolated microsomes with 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS) resulted in inhibition of ATP- and anion-dependent calcium uptake. A lipid-permeable organic acid such as maleate retained its ability to promote calcium uptake in DIDS-treated microsomes. However, a lipophilic anion, such as nitrate, stimulated calcium uptake only in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP). In addition, 2 microM valinomycin, when added in the absence or presence of 10 to 100 mM K+, had no stimulatory effect on calcium uptake. These results appear to be consistent with a model in which the active uptake of calcium into microsomes involves electroneutral Ca2+-nH+ exchange.
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16
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Calcium sequestration activity in rat liver microsomes. Evidence for a cooperation of calcium transport with glucose-6-phosphatase. BIOCHIMICA ET BIOPHYSICA ACTA 1985; 816:267-77. [PMID: 2988615 DOI: 10.1016/0005-2736(85)90494-8] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Mechanisms regulating the energy-dependent calcium sequestering activity of liver microsomes were studied. The possibility for a physiologic mechanism capable of entrapping the transported Ca2+ was investigated. It was found that the addition of glucose 6-phosphate to the incubation system for MgATP-dependent microsomal calcium transport results in a marked stimulation of Ca2+ uptake. The uptake at 30 min is about 50% of that obtained with oxalate when the incubation is carried out at pH 6.8, which is the pH optimum for oxalate-stimulated calcium uptake. However, at physiological pH values (7.2-7.4), the glucose 6-phosphate-stimulated calcium uptake is maximal and equals that obtained with oxalate at pH 6.8. The Vmax of the glucose 6-phosphate-stimulated transport is 22.3 nmol of calcium/mg protein per min. The apparent Km for calcium calculated from total calcium concentrations is 31.9 microM. After the incubation of the system for MgATP-dependent microsomal calcium transport in the presence of glucose 6-phosphate, inorganic phosphorus and calcium are found in equal concentrations, on a molar base, in the recovered microsomal fraction. In the system for the glucose 6-phosphate-stimulated calcium uptake, glucose 6-phosphate is actively hydrolyzed by the glucose-6-phosphatase activity of liver microsomes. The latter activity is not influenced by concomitant calcium uptake. Calcium uptake is maximal when the concentration of glucose 6-phosphate in the system is 1-3 mM, which is much lower than that necessary to saturate glucose-6-phosphatase. These results are interpreted in the light of a possible cooperative activity between the energy-dependent calcium pump of liver microsomes and the glucose-6-phosphatase multicomponent system. The physiological implications of such a cooperation are discussed.
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Fleschner CR, Kraus-Friedmann N, Wibert GJ. Phosphorylated intermediates of two hepatic microsomal ATPases. Biochem J 1985; 226:839-45. [PMID: 3157373 PMCID: PMC1144784 DOI: 10.1042/bj2260839] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The hepatic microsomal Ca2+- and Mg2+-dependent ATPase phosphoenzyme intermediates were distinguished by using the chelators EGTA and CDTA (trans-cyclohexane-1,2-diamine-NNN'N'-tetra-acetic acid). The Ca2+-ATPase intermediate is a hydroxylamine-labile base-labile 125 000-Mr phosphoprotein. The Mg2+-ATPase intermediate is a hydroxylamine-stable base-stable 30 000-Mr phosphoprotein. This enzyme intermediate probably reflects the large basal ATPase activity of hepatic microsomal fraction. It is dependent on Mg2+, since formation of the phosphoenzyme is abolished in the presence of CDTA. Under these conditions, the basal ATPase activity is dramatically decreased. These data demonstrate two separate and distinct enzymes which are responsible for the two ATPase activities of hepatic microsomal fraction. Furthermore, these data indicate that more meaningful data about the microsomal Ca2+-ATPase might be obtained if the free ion concentrations are controlled with CDTA.
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18
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Reaction mechanism of the calcium-transport ATPase in endoplasmic reticulum of rat liver. Demonstration of different reactive forms of the phosphorylated intermediate. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(20)71167-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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19
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Abstract
Exposure of isolated rat liver cells to glucagon or dibutyryl cyclic AMP leads to a prompt decrease in the rate of cellular peroxide generation as evidenced by (i) a reduced rate of [14C]formate oxidation and (ii) a lowered steady-state concentration of catalase Compound I.
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20
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The calcium pump in rat liver endoplasmic reticulum. Demonstration of the phosphorylated intermediate. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(18)90632-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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21
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Studer RK, Snowdowne KW, Borle AB. Regulation of hepatic glycogenolysis by glucagon in male and female rats. Role of cAMP and Ca2+ and interactions between epinephrine and glucagon. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43135-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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22
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Moore PB, Kraus-Friedmann N. Hepatic microsomal Ca2+-dependent ATPase. Calmodulin-dependence and partial purification. Biochem J 1983; 214:69-75. [PMID: 6225427 PMCID: PMC1152211 DOI: 10.1042/bj2140069] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The hepatic microsomal fraction contains tightly bound calmodulin as demonstrated by affinity chromatography. When this calmodulin was partially removed by EGTA treatment (0.5 mM-EGTA), the uptake of 45Ca2+ by the microsomal vesicles was stimulated by added calmodulin and inhibited by trifluoperazine (TFP). The Ca2+-dependent ATPase was partially purified on a calmodulin column. This partial purification resulted in a 500-fold increase in the specific activity of the enzyme when measured in the presence of added calmodulin. Antibodies prepared against calmodulin prevented this stimulatory effect. The fraction eluted from the calmodulin column contained several protein bands indicating that the specific activity of the Ca2+-dependent ATPase is probably still underestimated. There are likely to be other calmodulin-sensitive processes present in the hepatic microsomal fraction.
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Kraus-Friedmann N, Zimniak P. 45Ca2+ uptake and phospholipid methylation in isolated rat liver microsomes. Cell Calcium 1983; 4:139-50. [PMID: 6352045 DOI: 10.1016/0143-4160(83)90030-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The effects of glucagon, epinephrine and insulin on hepatic phospholipid methylation were studied. Glucagon, either injected into rats or added to perfused livers, stimulated methylation in subsequently isolated microsomes. Epinephrine also increased phospholipid methylation. Insulin by itself did not influence the rate of the reaction, but, when administered prior to glucagon, it blocked the effect of the latter. The possibility that the observed stimulation of phospholipid methylation might be causally linked to the reported stimulation by glucagon of 45Ca2+ uptake in subsequently isolated liver microsomes was examined. Both the substrate and the competitive inhibitor of the methylation reaction, S-adenosylmethionine and S-adenosylhomocysteine, had profound effect on the rate of phospholipid methylation, without having comparable effects on Ca2+ uptake. S-adenosylmethionine in increasing concentration stimulated methylation four-fold, while no significant changes in 45Ca2+ uptake were seen. S-adenosylhomocysteine did not inhibit 45Ca2+ uptake even at levels causing more than 95% decrease in methylation. In conclusion, while both phospholipid methylation and 45Ca2+ uptake seem to be hormonally controlled, the correlation between these two processes was not sufficient to support the notion that the changes in 45Ca2+ uptake are caused by the changes in phospholipid methylation.
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Dawson AP, Fulton DV. Some properties of the Ca2+-stimulated ATPase of a rat liver microsomal fraction. Biochem J 1983; 210:405-10. [PMID: 6222732 PMCID: PMC1154238 DOI: 10.1042/bj2100405] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
1. The heavy microsomal fraction from rat liver apparently has very little Ca2+-stimulated ATPase activity, although it has an active, ATP-driven Ca2+ accumulation system. 2. The addition of ionophore A23187 to the ATPase assay, to allow continuous Ca2+ recycling during the assay time, reveals the presence of a substantial Ca2+-stimulated ATPase with Vmax. 160 nmol of Pi/10 min per mg of protein and Km for Ca2+ 0.19 microM. 3. The Ca2+-stimulated ATPase, but not the basal Mg2+-stimulated ATPase, is potently inhibited by orthovanadate. Both the Ca2+-stimulated ATPase and the vanadate inhibition are enhanced by the presence of Mg2+. 4. Ca2+-stimulated ATPase activity is not responsive to calmodulin or the calmodulin antagonist trifluoperazine.
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Baddams HM, Chang LB, Barritt GJ. Evidence that glucagon acts on the liver to decrease mitochondrial calcium stores. Biochem J 1983; 210:73-7. [PMID: 6405743 PMCID: PMC1154191 DOI: 10.1042/bj2100073] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
1. Mitochondria isolated from rats treated with glucagon for 60 min or lives perfused in the presence of glucagon for 10 min exhibited lower rates of 45Ca2+ exchange than did control mitochondria when this was measured under steady-state conditions in the presence of Mg2+, ATP, Pi and 0.13 microM- or 0.16 microM-free Ca2+ at pH 7.4 and at 25 degrees C or 37 degrees C. Under these conditions no significant difference in the rates of Ruthenium Red-induced 45Ca2+ efflux was observed. These results contrast with earlier work in which mitochondria isolated from glucagon-treated livers were shown to exhibit faster rates of Ca2+ uptake [Yamazaki (1975) J. Biol. Chem. 250, 7924-7930] and slower rates of spontaneous Ca2+ efflux [Hughes & Barritt (1978) Biochem. J. 176, 295-304] when these parameters were measured under different incubation conditions, including supra-physiological concentrations of free Ca2+ and the absence of added Mg2+ and ATP. 2. Perfusion of livers with glucagon before the addition of adrenaline or the Ca2+-selective ionophore A23187, to release Ca2+ from intracellular stores, decreased the amount of Ca2+ released by these agents. 3. Incubation of isolated hepatocytes in the presence of glucagon at 1.3 mM extracellular Ca2+ induced a small decrease in the plateau of the 45Ca2+-exchange curve obtained under steady-state conditions. 4. It is concluded that the actions of glucagon on liver mitochondrial Ca2+ transporters lead to a decrease, rather than an increase, in mitochondrial Ca2+ stores in the intact cell.
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Kraus-Friedmann N, Biber J, Murer H, Carafoli E. Calcium uptake in isolated hepatic plasma-membrane vesicles. EUROPEAN JOURNAL OF BIOCHEMISTRY 1982; 129:7-12. [PMID: 7160385 DOI: 10.1111/j.1432-1033.1982.tb07014.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
A liver plasma-membrane fraction capable of Ca2+ uptake was isolated. The fraction exhibited high Na+, K+-ATPase, low glucose-6 phosphatase activity, and transported alanine in a Na+-dependent fashion. The uptake of Ca2+ was ATP-dependent; UTP, GTP, or CTP did not substitute for ATP. The presence of oxalate did not significantly alter the rate of uptake. The pH optimum of the reaction was basic (no uptake was visible at pH 6.8). These properties are at variance with those of the endoplasmic reticulum Ca2+ uptake system, which is oxalate-dependent, and has an acid pH optimum. The ATP-dependent Ca2+ uptake has a Km(Ca2+) of 1.4 X 10(-8) M and a Vmax of transport of 30 nmol X mg protein-1 X min-1. No conclusive results were obtained on the calmodulin-sensitivity of the process: addition of calmodulin to the vesicles did not stimulate uptake, and the anti-calmodulin drug trifluoperazine had no inhibitory effect. However, another anti-calmodulin drug (R24571) had a limited, but statistically significant, inhibitory action. A partial release of the accumulated Ca2+ from the vesicles could be induced by the addition of Na+, and incubation of the vesicles in a high Na+ medium (as compared to high K+ medium) resulted in lower (about 25%) calcium uptake. Partial release of the accumulated Ca2+ could be induced also by the addition of H+. The releasing effect of H+, taken together with the absence of Ca2+ uptake at acid pH, suggests the possibility of a H+/Ca2+ exchange.
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Brattin WJ, Waller RL, Recknagel RO. Analysis of microsomal calcium sequestration by steady state isotope exchange. Enzyme kinetics and role of membrane permeability. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(18)33983-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Dawson AP. Kinetic properties of the Ca2+-accumulation system of a rat liver microsomal fraction. Biochem J 1982; 206:73-9. [PMID: 6812572 PMCID: PMC1158551 DOI: 10.1042/bj2060073] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
1. By using Ca-EGTA buffers, the Km for Ca2+ uptake into rat liver heavy microsomes (microsomal fraction) was found to be 0.2 microM free Ca2+. 2. In the absence of oxalate, these vesicles accumulate about 20 nmol of Ca2+/mg of protein. Efflux of Ca2+ from the vesicles is much faster at pH 7.6 than at pH 6.8, but does not apparently show saturation kinetics or any stringent requirement for external ions. 3. The steady-state distribution of Ca2+ between the microsomes and the medium in the presence of ATP and the absence of oxalate is dependent on Ca2+ load. When the vesicles are loaded to 50% capacity, the external free Ca2+ concentration is 70 nM. 4. The affinity of heavy microsomes for Ca2+ is such that is seems likely that they has a dominant role in the determination of cytoplasmic free Ca2+ concentrations.
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Yamada M, Miyaji H. Binding of sex hormones by male rat liver microsomes. JOURNAL OF STEROID BIOCHEMISTRY 1982; 16:437-46. [PMID: 7087471 DOI: 10.1016/0022-4731(82)90057-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
In vitro microsomes of adult male rats possess binding sites specific for 17 beta-hydroxy-5 alpha-androstan-3-one (5 alpha-DHT), estradiol-17 beta (E2-17 beta) and progesterone (Prog), respectively. The characteristics of these microsomal steroid binding were as follows: 1. The equilibrium dissociation constants were estimated to be 35.4, 9.94 and 25.2 nM for 5 alpha-DHT, E2-17 beta and Prog, respectively. The maximum numbers of binding sites were estimated to be 0.25, 0.12 and 6.43 pmol/mg of microsomal protein for 5 alpha-DHT, E2-17 beta and Prog, respectively. 2. The ligand specificities of microsomal binding for 5 alpha-DHT, E2-17 beta and Prog were similar to so-called cytosolic androgen-, estrogen-, and progestin-receptors, respectively, with the following two exceptions, namely, unlabeled Prog best inhibited the microsomal [3H]-5 alpha-DHT binding and unlabeled DES did not significantly inhibit microsomal [3H]-E2-17 beta binding. 3. These microsomal steroid binding capacities were not affected significantly by different incubation at 2 degrees and 36 degrees C. The steroid-binding components of microsomes in physiological saline (0.13 M-NaCl) were no longer soluble after 1 M-NaCl extraction. Our data suggest strongly that sex steroids may act on mammalian liver by specific binding to microsomes, which brings about changes of various cytoplasmic events, as well as by their specific binding to so-called cytosolic receptors, which ultimately brings about direct gene activations.
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Williamson JR, Cooper RH, Hoek JB. Role of calcium in the hormonal regulation of liver metabolism. BIOCHIMICA ET BIOPHYSICA ACTA 1981; 639:243-95. [PMID: 7039675 DOI: 10.1016/0304-4173(81)90012-4] [Citation(s) in RCA: 287] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Andia-Waltenbaugh AM, Tate CA, Friedmann NK. The effect of glucagon on the kinetics of hepatic mitochondrial calcium uptake. Mol Cell Biochem 1981; 36:177-84. [PMID: 7254203 DOI: 10.1007/bf02357035] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Previous work by this and other laboratories has shown that glucagon administration stimulates calcium uptake by subsequently isolated hepatic mitochondria. This stimulation of hepatic mitochondrial Ca2+ uptake by in vivo administration of glucagon was further characterized in the present report. Maximal stimulation of mitochondrial Ca2+ accumulation was achieved between 6-10 min after the intravenous injection of glucagon into intact rats. Under control conditions, Ca2+ uptake was inhibited by the presence of Mg2+ in the incubation medium. Glucagon treatment, however, appeared to obliterate the observed inhibition by Mg2+ of mitochondrial Ca2+ uptake. Kinetic experiments revealed the usual sigmoidicity associated with initial velocity curves for mitochondrial calcium uptake. Glucagon treatment did not alter this sigmoidal relationship. Glucagon treatment significantly increased the V max for Ca2+ uptake from 292 +/- 22 to 377 +/- 34 nmoles Ca2+/min per mg protein (n = 8) but did not affect the K 0.5, (6.5-8.6 microM). Since the major kinetic change in mitochondrial Ca2+ uptake evoked by glucagon is an increase in V max, the enhancement mechanism is likely to be an increase either in the number of active transport sites available to Ca2+ or in the rate of Ca2+ carrier movement across the mitochondrial membranes.
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Ponnappa BC, Williams JA. Comparison of 45Ca2+ uptake activity by microsomes from control and stimulated mouse pancreatic acini. Life Sci 1981; 28:2395-402. [PMID: 7253828 DOI: 10.1016/0024-3205(81)90506-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Kraus-Friedmann N, Zimniak P. Glucagon and epinephrine-stimulated phospholipid methylation in hepatic microsomes. Life Sci 1981; 28:1483-8. [PMID: 7242243 DOI: 10.1016/0024-3205(81)90380-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Reinhart PH, Bygrave FL. Glucagon stimulation of ruthenium red-insensitive calcium ion transport in developing rat liver. Biochem J 1981; 194:541-9. [PMID: 6171260 PMCID: PMC1162778 DOI: 10.1042/bj1940541] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The maturation of glucagon-stimulated Ruthenium Red-insensitive Ca2+-transport activity was determined in livers of rats ranging in age from 5 days preterm to 10 weeks of adult life. Previous indications are that this activity is confined to vesicles derived mainly from the endoplasmic reticulum. Perinatal-rat liver contains near-adult values of Ruthenium Red-insensitive Ca2+-transport activity, and exhibits large transient increases in the rate of this activity at two stages of development, immediately after birth, and at 2-5 days after birth. The administration of glucagon to foetal rats, at developmental stages after 19.5 days of gestation (2.5 days before birth), results in a large stable increase (greater than 100%) of Ca2+-transport activity in a subsequently isolated 'heavy' microsomal fraction. That this fraction was enriched in vesicles derived from the rough endoplasmic reticulum was indicated by both an electron-microscopic examination and a marker-enzyme analysis of the subcellular fractions. The administration of glucagon into newborn animals only hours old does not enhance further the initial rate of Ca2+-transport activity, and from day 1 to 10 weeks after birth the administration of the hormone results in the moderate enhancement of Ca2+ transport. Experiments with cyclic AMP and inhibitors of phosphodiesterase activity suggest that cyclic AMP plays a key role in the enhancement by glucagon of Ruthenium Red-insensitive Ca2+ transport, and arguments are presented that this transport system has an important metabolic role in the redistribution of intracellular Ca2+ in liver tissue.
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