AJP - Endocrinology and Metabolism, Vol 269, Issue 5 E846-E851, Copyright © 1995 by American Physiological Society
Attenuation of glycogenolytic action of activin A in intact rat liver
I. Kojima, R. Nobusawa, Y. Q. Zhang, N. Sekine, T. Mine and H. Shibata
Department of Cell Biology, Gunma University, Maebashi, Japan.
Activin A stimulates glucose production by causing glycogenolysis in
isolated hepatocytes. To determine the physiological significance of this
effect, we examined the effect of activin A on glucose production in the
perfused 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 perfused in
the opposite direction. Although activin A did not promote glucose
production, it was recovered from the hepatic vein in a bioactive form.
When liver perfusion was performed in partially hepatectomized rats,
activin A increased radiocalcium efflux. In isolated hepatocytes, activin A
increased inositol phosphates, and the effect of activin A was attenuated
by the plasma membrane fraction of hepatocytes. The inhibitory effect of
the plasma membrane was abolished by digestion of the membrane with
trypsin. These results indicate that the effect of activin A on glucose
production is attenuated in the intact liver and that a protein factor(s)
in plasma membrane may be involved in the inhibition.
