Mechanism of glycogenolytic action of histamine in rat hepatocytes

1991 ◽  
Vol 261 (6) ◽  
pp. G1000-G1004 ◽  
Author(s):  
T. Mine ◽  
I. Kojima ◽  
E. Ogata
Keyword(s):  
Calcium Release ◽  
Rat Hepatocytes ◽  
Free Calcium ◽  
Maximal Effect ◽  
Dependent Manner ◽  
H2 Receptor Antagonist ◽  
Free Calcium Concentration ◽  
Messenger System ◽  
Glucose Output ◽  
Dose Dependent

The mechanism by which histamine induces glycogenolysis was investigated in rat hepatocytes. Histamine induced stimulation of glucose output in hepatocytes in a dose-dependent manner. The maximal effect of the glycogenolytic action of histamine, which was approximately 60% of the maximal glucagon action, was obtained at 10(-6) M. These effects were inhibited by H1 receptor antagonists triprolidine hydrochloride and tripelennamine but not by a H2 receptor antagonist cimetidine. Histamine also increased the activity of phosphorylase a. When 10(-6) M histamine and 5 x 10(-9) M glucagon were added simultaneously, the actions of these two agents were additive. In contrast, there was no additivity when 10(-6) M histamine and 10(-8) M angiotensin II were added. Histamine did not increase adenosine 3',5'-cyclic monophosphate at any doses tested but induced a rapid increase in the cytoplasmic free calcium concentration ([Ca2+]c). Histamine increased [Ca2+]c even in the presence of 1 microM extracellular calcium, an observation suggesting that histamine caused calcium release from an intracellular calcium pool(s). When [3H]inositol-labeled hepatocytes were incubated with histamine, radioactivity in the D-myo-inositol trisphosphate fraction was rapidly increased. These results indicate that histamine acts on rat hepatocytes mainly via H1 receptors and stimulates glycogenolysis by activating the calcium messenger system.

scholarly journals Calcium rather than cyclic AMP is an intracellular messenger of parathyroid hormone action on glycogen metabolism in isolated rat hepatocytes

1989 ◽  
Vol 258 (3) ◽  
pp. 889-894 ◽  
Author(s):  
T Mine ◽  
I Kojima ◽  
E Ogata
Keyword(s):  
Parathyroid Hormone ◽  
Cyclic Amp ◽  
Glucose Production ◽  
Rat Hepatocytes ◽  
Free Calcium ◽  
Dependent Manner ◽  
Isolated Rat Hepatocytes ◽  
Glucose Output ◽  
Dose Dependent ◽  
Isolated Rat

The synthetic 1-34 fragment of human parathyroid hormone (1-34hPTH) stimulated glucose production in isolated rat hepatocytes. The effect of 1-34hPTH was dose-dependent and 10(10) M-1-34 hPTH elicited the maximum glucose output, which was approx. 80% of that by glucagon. Although 1-34hPTH induced a small increase in cyclic AMP production at concentrations higher than 10(-9) M, 10(-10) M-1-34hPTH induced the maximum glucose output without significant elevation of cyclic AMP. This is in contrast to the action of forskolin, which increased glucose output to the same extent as 10(-10) M-1-34hPTH by causing a 2-fold elevation of cyclic AMP. In addition to increasing cyclic AMP, 1-34hPTH caused an increase in cytoplasmic free calcium concentration ([Ca2+]c). When the effect of 1-34hPTH on [Ca2+]c was studied in aequorin-loaded cells, low concentrations of 1-34hPTH increased [Ca2+]c: the 1-34hPTH effect on [Ca2+]c was detected at as low as 10(-12) M and increased in a dose-dependent manner. 1-34hPTH increased [Ca2+]c even in the presence of 1 microM extracellular calcium, suggesting that PTH mobilizes calcium from an intracellular pool. In line with these observations, 1-34hPTH increased the production of inositol trisphosphate. These results suggest that: (1) PTH activates both cyclic AMP and calcium messenger systems and (2) PTH stimulates glycogenolysis mainly via the calcium messenger system.

P2 purinoceptor localization along rat nephron and evidence suggesting existence of subtypes P2Y1 and P2Y2

1998 ◽  
Vol 274 (6) ◽  
pp. F1006-F1014 ◽  
Author(s):  
Seok Ho Cha ◽  
Takashi Sekine ◽  
Hitoshi Endou
Keyword(s):  
Calcium Concentration ◽  
Free Calcium ◽  
Dependent Manner ◽  
Reactive Blue 2 ◽  
Collecting Tubule ◽  
Single Nephron ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration ◽  
Dose Dependent ◽  
Cortical Collecting Tubule

Effects of extracellular ATP on intracellular free calcium concentration ([Ca2+]i) were examined in rat single nephron segments using the fura 2-AM. ATP (10 μM) induced a significant transient increase in [Ca2+]iin the glomerulus, the early proximal convoluted tubule (S1), the cortical collecting tubule (CCT), and the outer medullary collecting tubule (OMCT). The magnitude of the response was the greatest in the OMCT among four segments. ATP induced an increase in the [Ca2+]iin a dose-dependent manner in S1 and OMCT. In the OMCT, ATP caused a biphasic increase in [Ca2+]iconsisting of an initial rapid rise and a sustained phase. Removal of calcium from the medium resulted in an attenuation of the sustained phase of [Ca2+]iand an ∼30% reduction in the height of the initial [Ca2+]ipeak in response to 10 μM ATP. Effects of ATP, its analogs, and its metabolites were tested in the S1 and OMCT. ATP, 2-methylthio-ATP (2-MeS-ATP), ADP, and UTP increased [Ca2+]idose dependently. AMP and adenosine did not affect [Ca2+]iin the S1 and OMCT. The ATP- or 2-MeS-ATP-induced [Ca2+]iincrease was inhibited by the pretreatment of the S1 and OMCT with suramin or reactive blue 2. Neomycin, a phospholipase C inhibitor, attenuated the ATP-induced [Ca2+]iincrease. To investigate the hormonelike action of ATP in OMCT, a heterologous cross desensitization was performed. The pretreatment of OMCT with ATP inhibited increases in vasopressin-, ANG II-, endothelin-1-, or bradykinin-induced [Ca2+]iincrease. These findings suggest that ATP might affect the above peptidyl agonist-activated calcium mobilizations.

Abstract 272: Sex Differences in β-Adrenergic Responsiveness of Excitation-Contraction Coupling in Isolated Rabbit Hearts

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Gregory Hoeker ◽  
Ashleigh Hood ◽  
Rodolphe Katra ◽  
Steven Poelzing ◽  
Steven Pogwizd
Keyword(s):  
Sex Differences ◽  
Action Potentials ◽  
Adrenergic Receptor ◽  
Calcium Release ◽  
Dependent Manner ◽  
Ectopic Activity ◽  
Dose Threshold ◽  
Ectopic Beats ◽  
Cardioprotective Effects ◽  
Dose Dependent

Introduction: Sex differences in β-adrenergic receptor (β-AR) responsiveness are associated with female cardioprotection. We hypothesize that female (F) rabbits have reduced responsiveness to β-AR stimulation vs males (M), and that the degree and type of sex differences vary with the β-AR subtypes that are activated. Methods: Ventricular action potentials (AP) and intracellular calcium transients (CaT) were optically mapped from the epicardial surface of rabbit hearts during 3 Hz pacing. Spontaneous calcium release (SCR) and ectopic activity were elicited at 1, 3, and 5.5 Hz. β-responsiveness was assessed with the nonselective β-agonist isoproterenol (Iso, 1-316 nM), or β2-AR selective agonist zinterol (Zin, 10 nM). Results: At baseline, the time constant of CaT decay (τ) was faster in F than M (54.0±1.7 vs 62.1±3.0 ms; n=14, 14; p < 0.05), with no sex difference in CaT duration (CaD80). AP duration (APD90) was shorter in F than M (202.5±5.0 vs 218.2±5.7 ms; p < 0.05). Iso decreased τ, CaD80, and APD90 in a dose-dependent manner in both sexes (n = 5, 5 for F, M). Iso decreased τ to a lesser extent in F than M for 1 and 32-316 nM Iso (F = 11-32 ms, M = 23-48 ms; p < 0.05). The Iso-induced decrease in CaD80 was not significantly different in F than M at any dose. The Iso-induced decrease in APD90 was significantly less in F than M only at 316 nM Iso (75.5±8.7 ms vs 103.9±6.2 ms, p < 0.05). In contrast, there were no sex differences in the response to Zin for τ, CaD80, or APD90 (n = 6, 6 for F, M). Zin decreased τ by 7.2±2.0 ms in F vs 12.7±3.7 ms in M; CaD80 by 18.0±5.3% in F vs 21.1±8.0 ms in M; and APD90 by 24.9±8.5 ms in F vs 21.9±8.9 ms in M. SCR was observed in 50% (6/12) of hearts treated with Zin, whereas Iso elicited SCR in all hearts (10/10) with a dose threshold of 32 nM. No ectopic beats were observed with Zin (0/36 trials in 12 hearts). With Iso, ectopic activity was less frequent in F hearts (16%, 12/75 trials in 5 hearts) than in M hearts (41%, 26/68 trials in 5 hearts, p < 0.05). Conclusions: These results suggest that sex differences in AP and CaT depend on the dose of the agonist used and the β-AR subtypes that are activated. Elucidating nuances of sex differences in β-AR subtype physiology will provide a better understanding of the mechanisms of reduced β-responsiveness in F and its cardioprotective effects.

scholarly journals Insulin-responsive cultured foetal-rat hepatocytes. Their preparation and characterization

1984 ◽  
Vol 223 (1) ◽  
pp. 39-46 ◽  
Author(s):  
D C DeSante ◽  
L Little ◽  
D E Peavy ◽  
F Vinicor
Keyword(s):  
Monolayer Culture ◽  
Cultured Cells ◽  
Rat Hepatocytes ◽  
Dependent Manner ◽  
Deoxyribonuclease I ◽  
Haematopoietic Cells ◽  
Foetal Rat ◽  
The Relationship ◽  
Dose Dependent ◽  
Scatchard Plots

An improved non-perfusion method for the preparation of cultured foetal-rat hepatocytes is described. Digestion of the liver with collagenase and deoxyribonuclease I gave yields of 40 × 10(6) hepatocytes/g of liver. The plating efficiency of hepatocytes in medium with 10 microM-cortisol was 50%. Cell morphology and metabolism were maintained through 3 days of monolayer culture, with minimal contamination by haematopoietic cells or fibroblasts. The cultured cells bound and degraded 125I-insulin in a time- and dose-dependent manner. The estimated ED50 for competitive binding at 37 degrees C was 1.1 nM. Curvilinear Scatchard plots were observed, with estimates of 16 500 high-affinity sites (Kd = 813 pM) and 53 000 low-affinity sites (Kd = 23 nM) per cell. The cultured cells demonstrated a glycogenic response to insulin, with an estimated ED50 of 120 pM. The degree of glycogenic response to insulin varied with time in culture: 500% above basal on day 1, 200% on day 2, and only 150% on day 3. Cultured foetal cells also exhibited a time-dependent uptake of 2-aminoisobutyric acid, which, in contrast with previous reports with adult cells, was not stimulated by the presence of 10 nM-insulin. Cultured foetal hepatocytes may provide an interesting model with which to study the relationship between insulin-receptor binding and insulin action.

Tolbutamide inhibits glucagon-induced phosphorylation of 6PF-2-K/Fru-2,6-P2ase in rat hepatocytes

1995 ◽  
Vol 268 (3) ◽  
pp. E391-E396
Author(s):  
H. Ayame ◽  
A. Matsutani ◽  
H. Inoue ◽  
T. Kaneko ◽  
K. Kaku
Keyword(s):  
Rat Hepatocytes ◽  
Bifunctional Enzyme ◽  
Dependent Manner ◽  
Enzyme Protein ◽  
Dependent Protein ◽  
Sulfonylurea Drugs ◽  
Dose Dependent ◽  
Increased Activity ◽  
Reduced Activity

In previous studies, we demonstrated that tolbutamide inhibits a phosphorylation of hepatic 6-phosphofructo-2-kinase (6PF-2-K)/fructose-2,6-bisphosphatase (Fru-2,6-P2ase) catalyzed by the adenosine 3',5'-cyclic monophosphate-dependent protein kinase in a reconstruction system using the purified enzyme from the rat liver. In the current study, to assess a role of tolbutamide on hepatic 6PF-2-K/Fru-2,6-P2ase physiologically, we used intact rat hepatocytes and examined effects of tolbutamide on a phosphorylation of the bifunctional enzyme in the presence of glucagon. Glucagon induced a rapid phosphorylation of hepatic 6PF-2-K/Fru-2,6-P2ase accompanied by an inhibition of 6PF-2-K activity and a stimulation of Fru-2,6-P2ase activity in a dose-dependent manner. Tolbutamide inhibited glucagon-induced phosphorylation of the bifunctional enzyme protein in a dose-dependent manner. By adding 2 mM tolbutamide, reduced activity of 6PF-2-K and increased activity of Fru-2,6-P2ase in the presence of 10(-9) M glucagon were partially restored. The present results suggest the possibility that tolbutamide modulates the activity of hepatic 6PF-2-K/Fru-2,6-P2ase through inhibiting a phosphorylation of the enzyme protein. The counterregulatory influence of tolbutamide on the effect of glucagon suggests a possible mechanism for the extrapancreatic effect of sulfonylurea drugs.

Endothelin 1 increases cell calcium in mouse collecting tubule cells

1991 ◽  
Vol 261 (4) ◽  
pp. F720-F725 ◽  
Author(s):  
M. Naruse ◽  
S. Uchida ◽  
E. Ogata ◽  
K. Kurokawa
Keyword(s):  
Free Calcium ◽  
Second Phase ◽  
Endothelin 1 ◽  
Single Nephron ◽  
Heterologous Desensitization ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration ◽  
Collecting Tubules ◽  
Dose Dependent ◽  
Homologous Desensitization

Effects of endothelin 1 (ET-1) on intracellular free calcium concentration ([Ca2+]i) were examined in superfused single-nephron segments dissected from mouse kidney. ET-1, 10(-9) to 10(-6) M, caused a biphasic increase in [Ca2+]i consisting of an initial rapid rise followed by a second more sustained elevation in [Ca2+]i in cortical collecting tubules (CCT), outer medullary CT (OMCT), and inner medullary CT (IMCT). The magnitude of the response was dose dependent and was greater in CCT than in OMCT or IMCT. Additional studies using CCT revealed that Ca2+ removal from the superfusate resulted in attenuation of the second phase of [Ca2+]i with approximately 50% reduction in the height of the initial [Ca2+]i peak in response to 10(-6) M ET-1. Ca2+ channel blocker nicardipine had little effect on ET-1-evoked changes in [Ca2+]i. BAY K 8644 and high superfusate K+ also did not affect [Ca2+]i. Addition of ET-1 and arginine vasopressin (AVP), 10(-6) M each, showed the presence of homologous desensitization but the absence of heterologous desensitization in [Ca2+]i changes. There was no additive effect of ET-1 and AVP on [Ca2+]i when they were added together. These data show that ET-1 evokes a biphasic increase in [Ca2+]i of collecting tubules and suggest that the initial peak of the ET-1-evoked rise in [Ca2+]i is largely due to cell Ca2+ release and that the second sustained rise in [Ca2+]i is largely due to increased Ca2+ influx. Data also suggest that ET-1 and AVP may act in the collecting tubules through different receptors.

Oxytocin affects apical sodium conductance in rabbit cortical collecting duct

1993 ◽  
Vol 265 (4) ◽  
pp. F487-F503 ◽  
Author(s):  
T. Inoue ◽  
M. Naruse ◽  
M. Nakayama ◽  
K. Kurokawa ◽  
T. Sato
Keyword(s):  
Receptor Antagonist ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Physiological Role ◽  
Free Calcium ◽  
Second Phase ◽  
Dependent Manner ◽  
Cortical Collecting Duct ◽  
Acetoxymethyl Ester ◽  
Dose Dependent

The physiological role of oxytocin (OT) in the kidney is still unclear, although autoradiographic data have shown the existence of OT receptors in the rat kidney. We examined the effect of OT in the microperfused rabbit cortical collecting duct (CCD) by using conventional cable analysis and microscope photometry. On addition of 10(-9) M OT to the bath, the lumen-negative transepithelial voltage (VT) transiently increased and the transepithelial resistance (RT) and the fractional resistance of the apical membrane (FRA) (1st phase) both decreased. After this initial change, the lumen-negative VT gradually decreased below its baseline level and RT and FRA (second phase) both increased. These electrical changes were dose dependent and were prevented by the addition of 10(-5) M amiloride to the lumen. Although responses to OT were not prevented by 10(-9) M arginine vasopressin (AVP) or 10(-6) M of a V1-receptor antagonist (OPC-21268) or V2-receptor antagonist (OPC-31260), they were inhibited by the addition of the specific OT antagonist des-Gly-NH2-[d(CH2)3,Tyr(Me),Thr]OVT. Additional studies of intracellular free calcium ([Ca2+]i) revealed that 10(-8)-10(-6) M OT caused an increase in [Ca2+]i in CCD in a dose-dependent manner. Also, pretreatment with 2 x 10(-8) M bis-(aminophenoxy)ethane-tetraacetic acid-acetoxymethyl ester, an intracellular Ca2+ chelator, abolished the electrical and [Ca2+]i responses to OT. Pretreatment with 5 x 10(-4) M 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (CPT-cAMP) partially prevented the electrical responses to OT, thus reducing the decrease in lumen-negative VT below its basal level and the increase in RT after the 1st phase. These data show that OT affects the apical Na+ conductance of collecting duct cells through OT receptors distinct from the AVP receptors and that the effect of OT may, at least in part, be brought about by a mechanism(s) dependent on the increase in [Ca2+]i and cAMP production.

Vasopressin increases cytosolic free calcium in LLC-PK1 cells through a V1-receptor

1987 ◽  
Vol 253 (2) ◽  
pp. F328-F332 ◽  
Author(s):  
M. A. Burnatowska-Hledin ◽  
W. S. Spielman
Keyword(s):  
Parathyroid Hormone ◽  
Arginine Vasopressin ◽  
Calcium Concentration ◽  
Mdck Cells ◽  
Free Calcium ◽  
Base Line ◽  
Cytosolic Free Calcium ◽  
Free Calcium Concentration ◽  
Cytosolic Free Calcium Concentration ◽  
Dose Dependent

We examined the effects of arginine vasopressin (AVP), parathyroid hormone (PTH), and bradykinin (BK) on the cytosolic free calcium concentration ([Ca]i) in cultured LLC-PK1 and MDCK kidney cell lines by use of the fluorescent Ca chelator fura-2. In LLC-PK1 cells, the addition of AVP but not [1-desamino-8-D-arginine]vasopressin (dDAVP, V2 agonist), PTH, or BK (10(-6) M) caused a significant increase in [Ca]i. The AVP-induced increase in [Ca]i from 61 +/- 6 to 225 +/- 44 nM (n = 7, P less than 0.01) was rapid and transient, returning to base line in 2 to 3 min. The effect of AVP was dose dependent and was present at 1 (61% increase) but not 5 min after extracellular Ca was removed. The effect of 10(-6) M AVP could be blocked with the pressor (V1) antagonist, d(CH2)5Tyr(Me)AVP, but not dDAVP. In MDCK cells, BK, but not AVP and PTH, increased [Ca]i from 146 +/- 11 to 281 +/- 31 nM (n = 9, P less than 0.001). The removal of extracellular Ca (5 min), reduced but did not abolish this effect. These results indicate that [Ca]i mobilized by activation of V1-receptors may mediate AVP-regulated function in some transporting epithelia.

Cholinergic effects on intracellular free calcium concentration in renal corpuscle: role of parietal sheet

1992 ◽  
Vol 262 (2) ◽  
pp. F248-F255
Author(s):  
F. Lebrun ◽  
F. Morel ◽  
G. Vassent ◽  
J. Marchetti
Keyword(s):  
Calcium Release ◽  
Intracellular Free Calcium ◽  
Free Calcium ◽  
Response Curves ◽  
Glomerular Function ◽  
Intracellular Free Calcium Concentration ◽  
Free Calcium Concentration ◽  
External Calcium ◽  
Cholinergic Effects

To investigate a possible effect of cholinergic agonists on the renal glomerular function, fura-2 microfluorometric measurements of intracellular free calcium [( Ca2+]i) were performed on single intact glomeruli, single isolated parietal sheets of the Bowman's capsule and single parietal sheet-deprived glomeruli (PS-D glomerulus). Carbachol (10(-4) M), in the presence of 2 mM external calcium, induced a biphasic increase in [Ca2+]i characterized by a sharp initial peak followed by a sustained plateau in the whole glomerulus (delta [Ca2+]i = 177 +/- 13 and 70 +/- 7 nM, respectively; n = 21) and in the parietal sheet (418 +/- 30 and 111 +/- 13 nM, respectively; n = 21). In the PS-D glomerulus (n = 9), the response was less marked and included a barely visible peak (77 +/- 13 nM) and a relatively low plateau (49 +/- 11 nM). In the absence of external calcium, the peak phase was preserved in the three structures, indicating a calcium release from intracellular pools, whereas the plateau, due to the entry of external calcium, was suppressed. These effects were fully inhibited by 10(-4) M of either atropine or pirenzepine, demonstrating the muscarinic nature of the receptors. Dose-response curves showed that the parietal sheet was more sensitive to the physiological agonist (acetylcholine) than to carbachol. A still unexplained difference in sensitivity was noted between peak and plateau, respectively (half-maximal responses were 5 x 10(-6) vs. 5 x 10(-7) M for carbachol and 2 x 10(-7) vs. 3 x 10(-8) M for acetylcholine).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Genomic and nongenomic stimulatory effect of aldosterone on H+-ATPase in proximal S3 segments

2011 ◽  
Vol 300 (3) ◽  
pp. F682-F691 ◽  
Author(s):  
D. C. A. Leite-Dellova ◽  
G. Malnic ◽  
M. Mello-Aires
Keyword(s):  
Calcium Concentration ◽  
Free Calcium ◽  
Ru 486 ◽  
Nongenomic Action ◽  
Free Calcium Concentration ◽  
Cytosolic Free Calcium Concentration ◽  
Nongenomic Effects ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Cellular Acidification

The genomic and nongenomic effects of aldosterone on the intracellular pH recovery rate (pHirr) via H+-ATPase and on cytosolic free calcium concentration ([Ca2+]i) were investigated in isolated proximal S3 segments of rats during superfusion with an Na+-free solution, by using the fluorescent probes BCECF-AM and FLUO-4-AM, respectively. The pHirr, after cellular acidification with a NH4Cl pulse, was 0.064 ± 0.003 pH units/min ( n = 17/74) and was abolished with concanamycin. Aldosterone (10−12, 10−10, 10−8, or 10−6 M with 1-h or 15- or 2-min preincubation) increased the pHirr. The baseline [Ca2+]i was 103 ± 2 nM ( n = 58). After 1 min of aldosterone preincubation, there was a transient and dose-dependent increase in [Ca2+]i and after 6-min preincubation there was a new increase in [Ca2+]i that persisted after 1 h. Spironolactone [mineralocorticoid (MR) antagonist], actinomycin D, or cycloheximide did not affect the effects of aldosterone (15- or 2-min preincubation) on pHirr and on [Ca2+]i but inhibited the effects of aldosterone (1-h preincubation) on these parameters. RU 486 [glucocorticoid (GR) antagonist] and dimethyl-BAPTA (Ca2+ chelator) prevented the effect of aldosterone on both parameters. The data indicate a genomic (1 h, via MR) and a nongenomic action (15 or 2 min, probably via GR) on the H+-ATPase and on [Ca2+]i. The results are compatible with stimulation of the H+-ATPase by increases in [Ca2+]i (at 10−12-10−6 M aldosterone) and inhibition of the H+-ATPase by decreases in [Ca2+]i (at 10−12 or 10−6 M aldosterone plus RU 486).

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