PMID: 4017969Feb 1, 1985Paper

Difference in the mechanism of action of alpha-adrenergic agonists and vasopressin or angiotensin II in stimulating hepatic glycogenolysis; a role of extracellular calcium concentration

Endocrinologia Japonica
Y KoideK Yamashita

Abstract

The role of extracellular calcium in hormone-induced glycogenolysis was examined in a rat liver perfusion system by manipulating the perfusate calcium concentration and by using calcium antagonistic drugs. When the perfusate contained 1 mM CaCl2, 5 microM phenylephrine, 20 nM vasopressin, and 10 nM angiotensin II caused a persistent increase in glucose output and phosphorylase activity as well as a transient increase in 45Ca efflux from 45Ca preloaded liver. Verapamil hydrochloride (20-100 microM) inhibited the activation of glucose output by these hormones in a dose-dependent manner. This inhibitory effect was also associated with the inhibition of hormone-induced activation of phosphorylase and 45Ca efflux. In the absence of CaCl2 in the perfusate, the glycogenolytic effect of phenylephrine and its inhibition by verapamil were obtained equally as in the presence of CaCl2. However, the effects of vasopressin and angiotensin II were markedly attenuated and were not inhibited any further by verapamil. The substitution of diltiazem hydrochloride for verapamil produced essentially identical results. Cyclic AMP concentrations in the tissue did not change under any of these test conditions. The results indicate that the glycogenolyt...Continue Reading

Citations

Apr 21, 2009·American Journal of Physiology. Heart and Circulatory Physiology·Ramesh SaeediMichael F Allard

Related Concepts

Angiotensin II, Val(5)-
Argipressin Tannate
Calcium
Enzyme Activation
Extracellular Space
Glucose, (beta-D)-Isomer
Phosphorylases
Liver Glycogen
Nucleotides, Cyclic
Phenylephrine Hydrochloride

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