The podocyte cell coat in experimental nephrosis

We have investigated by light and electron microscopy the cell coat morphology of podocytes in rats with aminonucleoside-induced nephrotic syndrome. Blocks of tissue were stained before embedding with two different preparations of colloidal iron (CI) and with ruthenium red (RR). Ultrathin sections of Epon-embedded tissue were stained with acid solution of phosphotungstic acid (PTA) and with the periodic acid-silver methenamine technique (PASM). On light microscopy reduced stainability of the glomeruli after CI impregnation, as shown by the Prussian blue reaction, was evident in all the test animals as compared with controls. On electron microscopy the same CI techniques showed a well-preserved cell coat in all the test animals especially on the outer surface of podocytes. The same results were obtained with RR. This procedure stained also the lamina densa of the basement membrane and the thin cell coat of podocytes facing the basement membrane. In the PASM and PTA preparations, the cell coat was much thinner than after CI or RR and appeared as a continuous layer on the surface of podocytes in test and control animals. We suggest that the reduced CI staining is a consequence of the reduction of podocyte surface associated with foot process loss.