Quantitative electron microscopic autoradiography was employed to determine the changes in the binding of 125I-cationic ferritin (CFI, pI ~ 7.2 to 7.4) to the anionic sites of the glomerular basement membrane (GBM) of rats following the induction of nephrosis. Animals were rendered nephrotic by a single intravenous injection of puromycin aminonucleoside (PAN) and sacrificed 0, 7, 14, and 21 days after its administration. CFI (10 mg/mCi/100 g body weight) was given intravenously. The kidneys were subsequently fixed by perfusion and processed for electron microscopic autoradiography. The mean grain densities over the GBMs on 0, 7, 14, and 21 days of PAN nephrosis were 1.50 ± 0.04, 1.49 ± 0.05, 1.50 ± 0.05, and 1.51 ± 0.04, respectively. These results indicate that there are no significant alterations in the anionic sites rich in heparan sulfate proteoglycan during the entire course of PAN nephrosis.
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