Alterations in the basement membrane (heparan sulfate) proteoglycan in diabetic mice. Diabetes

tumor in normal and genetically diabetic mice (db/db) and measured some components of basement mem-brane produced in the tumor. These studies showed similar amounts of total protein in control and diabetic tissue and similar patterns of proteins on SDS gel electrophoresis of extracts of the tissue. Laminin, a basement membrane specific glycoprotein utilized as an attachment factor by epithelial cells, was present in increased amounts in diabetic tissue. In contrast, the amount of BM-1 (heparan sulfate) proteoglycan was reduced. Less 3SS-sulfate was incorporated into this proteoglycan, and the proteoglycan, but not its component glycosaminoglycans, was heterogeneous in size. The data indicate that either the synthesis of proteoglycan was decreased or its degradation was in-creased in diabetic tissue. Since the heparan sulfate proteoglycan serves to block the passage of anionic macromolecules through the basement membrane, decreased levels could account for the increased po-rosity of diabetic basement membrane. Compensatory synthesis of the basement membrane components to restore normal permeability could account for the thickened basement membranes observed in diabe-tes. DIABETES 37:185-188, February 1982. Basement membranes are thin extracellular matri-ces1 that separate epithelial and endothelial cellsfrom underlying stroma and prevent the passageof certain macromolecules.2"5 In diabetics, marked thickening of basement membranes is seen in cap-illaries and the kidney glomeruli and this change is be-lieved to underlie premature degeneration of the kidneys