Basement membrane components (7S collagen, laminin P1) are increased in sera of diabetics and activate platelets in vitro.

Serum concentrations of two basement membrane components (7S collagen and laminin P1) were detected by specific radioimmunoassays in 70 patients suffering from diabetes mellitus type I and II with and without clinical signs of microangiopathy. Serum levels of both antigens were increased compared to controls. 7S collagen concentrations were significantly different between the diabetics with signs of microvascular damage and those without small-vessel disease (p less than 0.05). Laminin P1 concentrations were also elevated, but the difference between the two groups of diabetics was not significant (p less than 0.2). Raised levels of circulating basement membrane proteins may indicate connective tissue activity and development of diabetic microangiopathy. In vitro 7S collagen is a moderate platelet activator inducing platelet spreading, aggregation, and malondialdehyde production. Laminin activates platelet spreading. As a part of the altered hemostatic system the activation of basement membrane components may contribute to the development of microvascular damage.