Abstract
To identify the role of Ca 2+ mobilization from intracellular pool(s) in the action of α-adrenergic agonist, the effects of dantrolene on phenylephrine-induced glycogenolysis were investigated in perfused rat liver. Dantrolene (5·10 −5 M) inhibited both glycogenolysis and 45Ca efflux induced by 5·10 −7 M phenylephrine. The inhibition by dantrolene was observed in the presence and absence of perfusate calcium. In contrast, dantrolene did not inhibit glycogenolysis induced by glucagon. To confirm the specificity of dantrolene action on calcium release in liver, experiments were also carried out using isolated hepatocytes. Dantrolene did not affect phenylephrine-induced production of inositol 1,4,5-trisphosphate. The compound did inhibit a rise in cytoplasmic Ca 2+ concentration induced by phenylephrine both in the presence and absence of extracellular Ca 2+. Thus, these results suggest that calcium release from an intracellular pool is essential for the initiation of α-adrenergic stimulation of glycogenolysis in the perfused rat liver.
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