Combined light and electron‐microscope morphometric studies of acute puromycin aminonucleoside nephropathy in rats

Morphometric observations were made on rats injected subcutaneously daily with puromycin aminonucleoside after two, four, six and eight daily injections. As a result it was possible to correlate the morphological alterations of the various glomerular components with the biochemical manifestations of the nephrotic syndrome particularly the onset of proteinuria. There was already significant loss of foot processes of the glomerular epithelial cells by the 2nd day, that is before the onset of proteinuria, suggesting that the loss of foot processes is a consequence of some metabolic impairment produced by the puromycin aminonucleoside which also subsequently causes the proteinuria. Swelling of the glomerular epithelial cells became significant by the 6th and 8th day of injection after the development of proteinuria, suggesting that it is a consequence of the increased amount of protein in the glomerular filtrate. Two independent morphometric methods suggest a decrease in the amount of glomerular basement membrane. Unfortunately because of difficulties in the determination of mean glomerular volumes it is not possible to be absolutely certain that this is a true finding, however it is what would be expected if the synthesis of basement membrane was depressed by the puromycin aminonucleoside.