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Rapid stimulation by vasopressin, oxytocin and angiotensin II of glycogen degradation in hepatocyte suspensions.

ABSTRACT: 1. The hormonal control of glycogen breakdown was studied in hepatocytes isolated from livers of fed rats. 2. Glucose release was stimulated by [8-arginine]vasopressin (10pm-10nm), oxytocin (1nm-1mum), and angiotensin II (1nm-0.1mum). These responses are all at least as sensitive to hormone as is glucose output in the perfused rat liver. 3. The effect of these three hormones on glucose release was critically dependent on extracellular Ca(2+), unlike that of glucagon. Half-maximal restoration of the vasopressin response occurred if 0.3mm-Ca(2+) was added back to the incubation medium. 4. Glycogen breakdown was more than sufficient to account for the glucose released into the medium, in the absence or presence of hormones. Lactate release by hepatocytes was not affected by vasopressin, but was inhibited by glucagon. 5. If Ca(2+) was omitted from the extracellular medium, vasopressin stimulated glycogenolysis, but not glucose release. 6. The phosphorylase a content of hepatocytes was increased by vasopressin, oxytocin and angiotensin II; minimum effective concentrations were 0.1pm, 0.1nm and 10pm respectively. This response was also dependent on Ca(2+). 7. These results demonstrate that hepatocytes can respond to low concentrations of vasopressin and angiotensin II, i.e. these effects are likely to be relevant in the intact animal. The role of extracellular Ca(2+) in the effects of these hormones on hepatic glycogenolysis and glucose release is discussed.

SUBMITTER: Hems DA

PROVIDER: S-EPMC1185697 | biostudies-other | 1978 May

REPOSITORIES: biostudies-other

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Stimulation by vasopressin, angiotensin and oxytocin of gluconeogenesis in hepatocyte suspensions.

Project description:1. In hepatocytes from starved rats, vasopressin, angiotensin (angiotensin II) and oxytocin stimulated gluconeogenesis from lactate by 25--50%; minimal effective concentrations were about 0.02pM, 1 nM and 0.2 nM respectively. 2. Vasopressin and angiotensin also stimulated gluconeogenesis from alanine, pyruvate, serine and glycerol. EGTA decreased gluconeogenesis from these substrates. 3. Hormonal stimulation of gluconeogenesis from lactate was abolished in the absence of extracellular Ca2+. 4. Insulin did not prevent stimulation of gluconeogenesis by vasopressin or angiotensin. 5. The potency of the stimulatory effects of vasopressin and angiotensin on hepatic gluconeogenesis suggests they are operative in vivo. Also, the data suggest that Ca2+ plays a role in the stimulation by these hormones.

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Oxytocin inactivates and phosphorylates rat hepatocyte glycogen synthase.

Project description:Incubation of isolated rat hepatocytes with oxytocin produces a time- and dose-dependent inactivation of glycogen synthase. Such inactivation is associated with an increase in the phosphorylation state of the 88 kDa subunit of the enzyme, as observed after electrophoretic analysis of the 32P-labelled enzyme isolated by immunoprecipitation from cells incubated with [32P]phosphate. CNBr cleavage of the immunoprecipitated glycogen synthase showed that multiple sites were phosphorylated after exposure of the cells to the hormone. The effect of oxytocin on hepatocyte glycogen synthase activity was not observed in the absence of extracellular Ca2+. Inactivation of glycogen synthase by oxytocin was partially abolished in the presence of insulin. These results indicate that the effects of oxytocin on glycogen synthase from rat hepatocytes are similar to those observed for other Ca2+-mediated glycogenolytic hormones, such as vasopressin.

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Glucagon, vasopressin and angiotensin all elicit a rapid, transient increase in hepatocyte protein kinase C activity.

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Myoblast stimulation with angiotensin II

Project description:Quiescent C2C12 myoblasts and myoblasts that were stimulated with Angiotensin II for 12 h or 24 h Keywords = Angiotensin II

2004-07-28 | E-GEOD-1592 | biostudies-arrayexpress

Myoblast stimulation with angiotensin II

Project description:Quiescent C2C12 myoblasts and myoblasts that were stimulated with Angiotensin II for 12 h or 24 h Keywords = Angiotensin II Keywords: parallel sample

2004-07-28 | GSE1592 | GEO

Multiple Aspects of Inappropriate Action of Renin-Angiotensin, Vasopressin, and Oxytocin Systems in Neuropsychiatric and Neurodegenerative Diseases.

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Developmental perspectives on oxytocin and vasopressin.

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Hyaluronan Production by Renomedullary Interstitial Cells: Influence of Endothelin, Angiotensin II and Vasopressin.

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