Unchanged Distribution Density of Anionic Sites on the Glomerular Wall in Rats with Streptozotocin-Induced Diabetic Nephropathy

As a cause of proteinuria in diabetic nephropathy, a decrease in anionic charge on the glomerular basement membrane (GBM) is considered to be related to protein leakage. However, the constancy of the anionic charge has been reported in several types of nephropathy. To elucidate the relation between glomerular protein leakage and anionic charge, we examined the distribution of anionic sites on the GBM and podocytes in diabetic rats induced by a single intravenous injection of 60 mg/kg of streptozotocin (STZ). Five months after the treatment with STZ, urinalysis for glucose and protein levels was conducted, and the kidneys were examined using electron microscopic cytochemistry for the assessment of anionic charge with two cationic probes. The distributions of anionic sites on the GBM demonstrated by two kinds of cationic markers in the diabetic rats were similar in density to those seen in the control animals. The distributions of anionic sites on the foot processes and cell membrane of podocytes were regular and also similar in density to that of the control group. From these results, we consider that the charge barrier of the GBM and podocytes is irrelevant to the protein leakage in diabetic rats.