AJP - Endocrinology and Metabolism, Vol 253, Issue 4 E395-E400, Copyright © 1987 by American Physiological Society
Altered contractile proteins in skeletal muscle of diabetic rats
P. K. Ganguly, Y. Taira, V. Elimban, M. Roy and N. S. Dhalla
Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada.
The ATPase activity of myofibrils and myosin from hindlimb muscle was
investigated in animals 4 wk after the induction of diabetes by an
intravenous injection of streptozotocin (65 mg/kg). Ca2+-stimulated ATPase
in myofibrils was increased in diabetic muscle at various times of
incubation (1-7 min) as well as at different concentrations of free Ca2+
(10(-7)-10(-5) M Ca2+). Such an increase in Ca2+-stimulated ATPase was
evident as early as 1 wk after streptozotocin injection, but Mg2+-ATPase
activity remained unaltered. Treatment of diabetic animals with insulin
Ca2+-ATPase and actin-activated ATPase activities of pure myosin were
similarly increased in diabetic muscle. Myosin ATPase was also activated by
K+- or NH4+-EDTA; these responses were more in diabetic muscle. However,
sodium dodecyl sulfate gel electrophoresis failed to reveal differences in
the patterns of contractile proteins, and pyrophosphate gels did not show
significant changes in myosin isozyme patterns between diabetics and
controls. The results of this study demonstrate an activation of
contractile protein ATPase of skeletal muscle in diabetes and seem to
indicate that such an alteration may be responsible for enhanced
contractile function of skeletal muscle in this disease.
