AJP - Endocrinology and Metabolism, Vol 257, Issue 1 E74-E80, Copyright © 1989 by American Physiological Society
Phosphorylase synthesis in diabetic hepatocytes and cardiomyocytes
J. Rulfs, S. R. Jaspers, A. K. Garnache and T. B. Miller Jr
Department of Biochemistry, University of Massachusetts Medical Center, Worcester 01655.
Whereas total cardiac glycogen phosphorylase activity appears to be
unaffected by severe insulin deficiency, a diabetes-induced decreased in
hepatic glycogen phosphorylase activity has been demonstrated by our
laboratory and others using liver extracts, isolated perfused liver, and
cultured hepatocytes. The loss of activity in diabetic liver can be
correlated with a drop in protein levels. Using primary cultures of cells
from normal and diabetic rats and phosphorylase specific antibodies, we
found a corresponding decrease in phosphorylase synthesis in diabetic
hepatocytes cultured for 2 days in a serum-free, chemically defined medium.
When hepatocytes are cultured in the presence of insulin, triiodothyronine,
and cortisol, there is a significant recovery in the rate of phosphorylase
synthesis after 3 days. Over the 3-day time period, there is no significant
difference in the rate of phosphorylase degradation in normal compared with
diabetic hepatocytes. Total protein synthesis in both hepatocytes and
cardiomyocytes is unaffected by diabetes, as is phosphorylase synthesis in
cultured cardiomyocytes.
