Alterations in Ca2+ binding by and composition of the cardiac sarcolemmal membrane in chronic diabetes.

Chronic streptozotocin-induced diabetes in rats was associated with a significant loss in the ability of isolated cardiac sarcolemmal membranes to bind Ca2+. Administration of insulin to the diabetic rats normalized the sarcolemmal Ca2+ binding capacity. The content of sialic acid residues, which are considered to represent a superficial Ca2+ pool in sarcolemma, was decreased in preparations from diabetic rats, and this change also was reversible upon insulin treatment of the diabetic rats. Treatment of sarcolemma with neuraminidase decreased Ca2+ binding by 37% in control preparations but had no effect on diabetic preparations. Diphosphatidylglycerol content was decreased but other acidic phospholipids such as phosphatidylinositol and phosphatidylserine, which also bind Ca2+, were not altered during diabetes. An increase in lysophosphatidylcholine and a decrease in phosphatidylethanolamine contents were observed in membranes isolated from diabetic rats. These results suggest that some alterations occur in Ca2+ binding and composition of heart sarcolemma in chronically diabetic rats and may provide further insight into the pathogenesis of diabetic cardiomyopathy.