Abstract
We studied alterations in diabetic heart muscle by the biochemical analysis of the sarcoplasmic reticulum (SR) and the structural proteins. Experimental diabetes mellitus was produced in rats by single intravenous injection of streptozotocin for 1 to 16 weeks (DM group) and insulin was injected subcutaneously for 2 to 4 weeks for rats selected as DM+I group. Fasting blood glucose was markedly elevated to greater than 400 mg/dl in DM group.In DM + I group, these levels were controlled 113.5 and 131.0 mg/dl on the average in rats of 2 and 4 weeks, respectively. Body and heart weights were significantly lesser at the time of sacrifice in DM group than in normal controls (C group) and DM+I group, but heart/body weight ratio was higher in DM group from 4 weeks. Both of Mgr++-and Cap++-ATPase activities of SR depressed significantly to 35 and 42 % of C group at 1 week in DM group, respectively, reduced further until 2 to 16 weeks. Cap-ATPase activity of structural proteins decreased gradually in DM group to 18 to 36 % of C group from 4 to 16 weeks. In SDS gel electrophoresis, the pattern of structural proteins in DM group was similar to that in C group, but in SR of DM group about 100 K dalton protein increased significantly from 4 weeks, suggesting an increase in the major ATPase protein. In DM+I group all of these alterations were inhibited significantly. These results indicate that SR is damaged in the early stage of diabetes, and induce relaxation disturbance in the diabetic heart.
