A stereologic study of glomerular hypertrophy in the subtotally nephrectomized rat.

Subtotal nephrectomy in the rat is followed by glomerular hypertrophy, glomerulosclerosis, and, ultimately, renal failure. To gain more insight into this sequence, we have made a morphometric study of the glomerular changes following subtotal nephrectomy in the rat during the period of functional compensation before glomerulosclerosis appears. We found a twofold increase in glomerular volume as compared with controls 2 weeks after operation (to approximately 2 X 10(6) cu mu) followed by a linear increase to approximately 5 X 10(6) cu mu at 21 weeks. The rate of increase in glomerular volume in controls did not significantly exceed that of body weight. The volume increase after subtotal nephrectomy is a true hypertrophy, since other morphometric parameters expressed per unit glomerular volume (surface and length densities) were approximately 80% of control values at 2 weeks and constant thereafter. Glomerular hypertrophy up to 21 weeks is accompanied by a stable BUN and a gradually increasing proteinuria. We conclude that glomerular hypertrophy in this system is a pathologic rather than a compensatory process and suggest that it may represent a counter-productive response to hemodynamic changes serving to increase the glomerular filtration rate.