Hepatic insulin effects independent of changes in Ca++ metabolism.
The possibility of Ca++ acting as second messenger for insulin in rat liver was investigated using the net stimulation of 14C-glucose incorporation into glycogen by isolated hepatocytes as an index of insulin action. An insulin effect could be partially sustained in the virtual absence of Ca++ and Mg++ and a maximal insulin effect could be observed in the presence of either Ca++ or Mg++, suggesting that extracellular Ca++ is not required for insulin action. Inhibiting the activity of calmodulin, an intracellular mediator of Ca++ action, with trifluoperazine had little effect on insulin action. The efflux of 45Ca from prelabeled hepatocytes was not altered by the presence of insulin arguing against insulin-induced changes in Ca++ fluxes. Collectively, these results do not support the role of Ca++ as second messenger for insulin action in liver.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D066298:In Vitro Techniques; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008112:Liver Glycogen / Q000096:biosynthesis; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D007328:Insulin; D008112:Liver Glycogen; D005947:Glucose; D002118:Calcium