AJP - Endocrinology and Metabolism, Vol 241, Issue 5 378-E384, Copyright © 1981 by American Physiological Society
Muscle proteolytic enzyme activities in diabetic rats
M. A. McElligott and J. W. Bird
Proteolytic enzyme activities were measured in skeletal muscle of
Sprague-Dawley rats with streptozotocin-induced diabetes [tail vein
injection of streptozotocin (100 mg/kg), under ether anesthesia]. Assay of
rat muscle homogenates from diabetic rats revealed a significant increase
in alkaline serine protease activity as compared to untreated control rats
and diabetic rats given insulin. There were no significant changes in
lysosomal cathepsin activities in diabetic muscle as compared to controls.
Gel studies of myofibrils isolated from the three groups of rats, subjected
to autolysis, revealed that the serine protease had copurified with the
myofibrils. Treatment of rats with compound 48/80, which degranulates mast
cells, abolished the alkaline protease activity. There was no serine
protease activity associated with the myofibrils isolated from compound
48/80-treated rats. Results from this study indicate that serine proteases
are not involved in muscle protein breakdown in diabetes and are of mast
cell origin.
