Urinary excretion of glycosaminoglycans and albumin in experimental diabetes mellitus

Diabetes mellitus was induced in one group of rats by a single injection of streptozotocin. The glycemia, the body weight, and the blood systolic pres sure were measured every week, and the 24 h urine volume and urinary excret ions of creatinine, albumin and glycosaminoglycans were measured every 2 we eks, At the end of the experiment (12 weeks) the weight and the glycosamino glycan composition of the kidneys were determined. All the diabetic animals were hyperglycemic, hypertense, and did not gain weight during all the exp erimental period. Albuminuria appeared from the second week on. Rat urine w as shown to contain heparan sulfate, chondroitin sulfate, and dermatan sulf ate, and the glycosaminoglycan excretion decreased in all diabetic animals. The onset of the change in glycosaminoglycan excretion rate was a very ear ly event, appearing in the second week after diabetes induction. The main g lycosaminoglycan found in normal rat kidney was heparan sulfate and, in con trast to the urine, the total kidney glycosaminoglycans increased in diabet ic kidney, due to chondroitin sulfate and dermatan sulfate accumulation. Th e heparan sulfate concentration (per tissue dry weight) did not change. Our results suggest that quantification of urinary glycosaminoglycans may be a useful tool for the early diagnosis of diabetic nephropathy.