Effects of secretin on glycogenolysis in cultured liver cells.

Upon incubation of hepatocyte isolated from rats with secretin at concentration ranging from 0.1 unit to 1.0 unit per ml, glycogenolysis was maximally stimulated after 15 min. Somatostatin inhibited liver glycogenolysis. The combined addition to the incubation medium showed that somatostatin inhibited the stimulated glycogenolysis induced by secretin, while secretin plus vasoactive intestinal peptide showed no additive effects on glycogenolysis, as compared with single addition of secretin. However, the addition of glucagon to secretin showed additive effects on glycogenolysis. These results suggest that the receptor site for secretin might be different from that for glucagon, but the same as that for vasoactive intestinal peptide. Moreover, the calcium ion was shown to be a prerequisite for the inducible effects of the hormones so far tested.