Changes in glomerular heparan sulfate in puromycin aminonucleoside nephrosis

Changes in glomerular anionic sites in puromycin aminonucleoside nephrosis (PAN) in the rat are controversial. The authors examined glomerular anionic sites in PAN by in vivo staining with polyethyleneimine (PEI). They also quantitated and characterized glomerular heparan sulfate (HS), which is known to be a major glomerular polyanion in PAN, using in vivo incorporation of 35S-sulfate. PAN rats had a mean protein excretion of 96 +/- 23 mg per 24 hours. Staining of anionic sites with PEI showed 15.3 +/- 2.8 sites per 1000-nm length of glomerular basement membrane in controls, 13.7 +/- 1.9 sites in PAN rats (P greater than 0.05), and 50% of rats with early PAN had absent staining. Total 35S-sulfate incorporation was similar in both the controls and established PAN rats (2900 +/- 150 dpm/mg dry wt of glomeruli versus 3005 +/- 260, P greater than 0.05) but decreased in early PAN rats (2025 +/- 148). The percentage of 35S-sulfate incorporated into chondroitin sulfate was similar in all three groups of animals. HS uronic acid was also similar (1.8 +/- 0.2 g/mg dry wt of glomeruli versus 1.7 +/- 0.3, P greater than 0.05) but decreased in early PAN (1.1 +/- 0.2). The distribution of 35S-sulfate activity within the HS subfractions was examined by ion-exchange chromatography and showed a shift in percent present from 1.0 M to 1.25 M fraction in established and early PAN animals (control 1.0 M 37% +/- 3.2% versus PAN 19% +/- 3.4%, P less than 0.01, and 1.25 M 36% +/- 2.9% versus 53% +/- 2.9%, P less than 0.01). These results demonstrate that glomerular heparan sulfate is unchanged in established PAN but decreased in early PAN. SO4 incorporation is unchanged in established PAN and diminished in early PAN. Thus, early in PAN HS synthesis is impaired, but in established PAN the HS is normal, and changes in glomerular HS cannot explain the increased permeability.