AJP - Heart and Circulatory Physiology, Vol 249, Issue 5 1024-H1030, Copyright © 1985 by American Physiological Society
Lipolysis in isolated myocardial cells from diabetic rat hearts
K. A. Kenno and D. L. Severson
Diabetes in rats was induced with streptozotocin (100 mg/kg); myocardial
cells (myocytes) were isolated from the hearts 3-4 days later. Diabetic
myocytes were characterized as having the same viability and ATP content as
control myocytes, but the yield was reduced. The triacylglycerol content of
diabetic myocytes was elevated by 3.7-fold; this resulted in an increased
rate of glycerol output during subsequent incubations. There was a
stoichiometric relationship between the decline in the cellular
triacylglycerol content and the release of glycerol into the incubation
medium. Isoproterenol stimulated the output of glycerol from control
myocytes by about twofold, but the stimulation of glycerol output from
diabetic myocytes by isoproterenol was markedly less. The combination of
1-methyl-3-isobutylxanthine with isoproterenol or
8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate also failed to
produce the same lipolytic response in diabetic myocytes as in control
myocytes. Triacylglycerol-loaded myocytes from control rats, prepared by
including palmitate in the isolation buffers, were also characterized as
having increased basal rates of glycerol output and a reduced lipolytic
response to isoproterenol. The level of free fatty acids in diabetic
myocytes was 2.8-fold greater than in myocytes from control hearts. The
intracellular accumulation of free fatty acids in these quiescent
populations of diabetic myocytes may limit the ability of catecholamines to
produce a further stimulation of lipolysis.
