AJP - Endocrinology and Metabolism, Vol 245, Issue 4 379-E383, Copyright © 1983 by American Physiological Society
Altered regulation of cardiac glycogen metabolism in spontaneously diabetic rats
T. B. Miller Jr
Isolated perfused hearts from control Bio-Breeding/Worcester (BB/W) rats
and spontaneously diabetic BB/W rats were studied to determine whether
metabolic abnormalities that are expressed in alloxan-diabetic rats in the
regulation of enzymes involved in glycogen metabolism could be observed in
this non-chemically induced insulin-deficient rat. Perfusion of hearts from
control rats with 10(-8) M insulin for 10 min resulted in activation of
glycogen synthase (30% synthase I without insulin to 44% synthase I with
insulin). Perfusion of hearts from BB/W diabetic rats demonstrated a lack
of acute synthase activation with insulin and a 45% decrease in synthase
phosphatase activity. Perfusion of hearts from BB/W diabetic rats with 0.28
microM epinephrine for 1 min resulted in a greater activation of
phosphorylase (44% phosphorylase a) than that observed in BB/W control
hearts (31% phosphorylase a) perfused under the same conditions.
Epinephrine produced similar changes in cyclic AMP accumulation, protein
kinase activation, and phosphorylase kinase activation in perfused hearts
of BB/W control and diabetic rats. Further, phosphorylase phosphatase
activities were not changed by epinephrine or insulin deficiency. These
studies further document metabolic abnormalities in the BB/W diabetic rat
that are attributable to insulin deficiency in a non-chemically induced
model for insulin-dependent diabetes.
