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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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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PMID:Oxytocin inactivates and phosphorylates rat hepatocyte glycogen synthase. 250 22

Exposure to phospholipase C increased the incorporation of [32P]Pi into phosphatidate, CMP-phosphatidate and phosphatidylinositol in rat adipose tissue and isolated adipocytes. A similar effect was observed in response to insulin and oxytocin. Theophylline, 3-isobutyl-1-methylxanthine and adenosine deaminase decreased [32P]Pi incorporation, and adenosine and N6-phenylisopropyladenosine reversed these effects. As with insulin, exposure of adipose tissue to phospholipase C stimulated oxidation of glucose, pyruvate and leucine and activated pyruvate dehydrogenase. Oxytocin and adenosine also mimicked the effects of insulin on leucine oxidation and pyruvate dehydrogenase. However, only insulin stimulated glycogen synthase activity, indicating that the regulation of synthase may be achieved by intracellular events distinct from those regulating changes in phospholipid metabolism, sugar transport and mitochondrial enzyme activities. It is postulated that exposure to phospholipase C forms diacylglycerol, which is phosphorylated to yield phosphatidate. The increased labelling of CMP-phosphatidate and phosphatidylinositol results from the conversion of phosphatidate into these lipids. The correlation between the effects of phospholipase C on phosphatidate synthesis and changes in adipose-tissue metabolism suggests the possibility that increased phosphatidate may directly or indirectly produce changes in membrane transport and enzyme activities. The pattern of phospholipid labelling produced by insulin, adenosine and oxytocin suggests that these stimuli may also increase phosphatidate synthesis, and, if so, changes in phospholipid metabolism could account for some of the metabolic actions of these stimuli.
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PMID:Phosphatidic acid and phosphatidylinositol labelling in adipose tissue. Relationship to the metabolic effects of insulin and insulin-like agents. 641 Oct 68

Oxytocin has both insulin-like and insulin antagonistic actions in fat cells in vitro. The anti-insulin-like effects of oxytocin in dispersed rat fat cells have been studied. The magnitude of the anti-insulin-like activity varies with the metabolic pathway of glucose utilization; oxidation [14CO2 production], 32%; glycogen synthesis (D-[U-14C] glucose incorporation into glycogen), 77%. In addition, direct inhibition of the activation of fat cell glycogen synthase has been shown. These inhibitory effects depend upon an intact disulfide ring, since the ability of N-ethylmaleimide-reacted oxytocin to inhibit insulin-stimulated processes was reduced by more than 90% when compared to the intact molecule.
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PMID:Oxytocin: anti-insulin-like effects in isolated fat cells. 643 35