Renal structural abnormalities following recovery from acute puromycin nephrosis

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Rats that recover from acute puromycin nephrosis later develop widespread glomerular and tubulointerstitial injury. The current study sought to identify structural changes present in the recovery phase that could precipitate progressive renal disease. Stereologic studies were performed 10 weeks after administration of puromycin (PAN) or saline (Cont). Serial sections were examined to assess glomerular structure. Rats receiving puromycin developed heavy proteinuria that returned nearly to control levels at 10 weeks. Kidneys in these animals were moderately enlarged and exhibited expansion of the interstitium (PAN, 254 +/- 47 mm3; Cont, 152 +/- 23 mm3; P < 0.05). The average glomerular volume was not different from control (PAN, 1.90 +/- 0.38 x 10(6) microm3; Cont, 2.07 +/- 0.47 x 10(6) microm3), but a subpopulation of glomeruli of about half normal size was found in PAN rats. Serial sections revealed that most of these glomeruli were not connected to normal tubule segments. Serial sections also revealed that more than 90% of glomeruli in rats recovering from nephrosis had synechias joining the tuft to Bowman's capsule. Synechias occupied an average of 8 +/- 11% of the Bowman's capsule surface in PAN animals versus less than 1% of the surface in controls. The appearance of synechias was not associated with a reduction in the mean number of visceral or parietal epithelial cells per glomerulus. Acute puromycin nephrosis does not cause a notable reduction in visceral epithelial cell number. However, widespread glomerular injury characterized by synechia between the tuft and Bowman's capsule is present following remission of proteinuria. Progression of this residual glomerular injury could contribute to the late development of glomerular segmental sclerosis following recovery from acute nephrosis.