Studies on collagen metabolism in rats. II. Turnover and amino acid composition of the collagen of glomerular basement membrane in diabetes mellitus.

The effects of streptozotocin diabetes on the collagen metabolism in rat glomerular basement membrane (GBM) have been investigated. The metabolic activity was measured in vivo by following the incorporation of 3H-proline into hydroxyproline over the course of 3 months. Under diabetic conditions, smaller amounts of labeled hydroxyproline were found in the GBM indicating that collagen synthesis is injured. The retarded disappearance of the tracer from the GBM is related to an additional alteration of the degradation resulting in a slower turnover. If collagen formation is reduced in streptozotocin diabetes, the thickening of the diabetic basement membranes can only explained by this disturbed catabolism. The amino acid composition of GBM was also altered after streptozotocin application. The diabetic animals showed an increase of hydroxylysine in this structure. The diabetic effects on the GBM presented were interpreted as a kind of accelerated aging of collagen.