AJP - Heart and Circulatory Physiology, Vol 249, Issue 5 1051-H1055, Copyright © 1985 by American Physiological Society
Abnormal cardiac biochemistry in spontaneously diabetic Bio-Breeding/Worcester rat
A. Malhotra, J. P. Mordes, L. McDermott and T. F. Schaible
Diabetes produced by injection of alloxan or streptozotocin results in
cardiac dysfunction in rats that is associated with lower cardiac
contractile protein ATPase activity. The purpose of this investigation was
to examine cardiac myosin biochemistry in the Bio-Breeding Worcester (BB/W)
rat, a strain in which diabetes occurs spontaneously and closely resembles
insulin-dependent diabetes in humans. Hearts from diabetic BB/W rats were
studied at 1, 4, and 7 mo after the onset of diabetes and were compared
with age-matched BB/W rats that were bred for resistance to diabetes.
Calcium-stimulated myosin ATPase activity was significantly decreased after
4 and 7 mo of diabetes, and actin-activated myosin ATPase was significantly
depressed at all time points. Differences between hearts from control and
diabetic animals increased with the duration of diabetes. Closely
associated with reductions in myosin ATPase activity in the diabetes was a
shift in the isomyosin content from the normally predominant V1 to the V3
isoenzyme. Thus diabetes that results from genetic causes leads to
depressed myosin enzymatic activity in the rat. Furthermore, since previous
studies have shown that BB/W diabetic rats do not develop hypothyroidism,
the present results support the view that altered thyroid function does not
mediate the abnormalities in cardiac contractile proteins in diabetes.
