Puromycin aminonucleoside nephrosis (PAN) results in a marked increase in the fractional clearance of
albumin. The increase in the fractional clearance of [(3)H]
albumin to approximately 0.045, as measured both in vivo and in the isolated perfused rat kidney (IPK) with PAN, occurs without an accompanying equivalent increase in glomerular capillary wall size selectivity as previously measured with
dextrans. This is very similar to the marked increase in
albuminuria seen with kidneys treated with inhibitors of endocytosis by the tubular epithelium, particularly
lysine (T. M. Osicka, L. M. Pratt, and W. D. Comper. Nephrology 2: 199-212, 1996). The similarity is further established that, like in the presence of
lysine, [(3)H]
albumin excreted in urine from rats with PAN is essentially intact whereas, in both in vivo and IPK control experiments, excreted [(3)H]
albumin is heavily degraded. The same observations have also been made for (3)H-labeled anionic
horseradish peroxidase. These observations suggest that the significant
albuminuria that occurs in PAN is primarily post-glomerular basement membrane in origin.