ATTENUATION OF GLYCOGENOLYTIC ACTION OF ACTIVIN-A IN INTACT RAT-LIVER

Attenuation of glycogenolytic action of activin A in intact rat liver. Am. J. Physiol. 269 (Endocrinol. Metab. 32): E846-E851, 1995.-Activin A stimulates glucose production by causing glycogenolysis in isolated hepatocytes. To determine the physiological significance of this effe ct, we examined the effect of activin A on glucose production in the p erfused Liver. Unlike the effect in isolated cells, activin A did not enhance glucose production nor did it cause radiocalcium efflux in the perfused liver. There was no effect of activin A in the liver perfuse d in the opposite direction. Although activin A did not promote glucos e production, it was recovered from the hepatic vein in a bioactive fo rm. When Liver perfusion was performed in partially hepatectomized rat s, activin A increased radiocalcium efflux. In isolated hepatocytes, a ctivin A increased inositol phosphates, and the effect of activin A wa s attenuated by the plasma membrane fraction of hepatocytes. The inhib itory effect of the plasma membrane was abolished by digestion of the membrane with trypsin. These results indicate that the effect of activ in A on glucose production is attenuated in the intact liver and that a protein factor(s) in plasma membrane may be involved in the inhibiti on.