Glomerular hypertrophy after subtotal nephrectomy: relationship to early glomerular injury

Abstract

Structural adaptations in response to approx. 70% nephrectomy were studied in male Sprague-Dawley rats. Rats developed systemic hypertension as well as progressive albuminuria after nephrectomy. At 18–26 weeks after nephrectomy (n=6) or sham treatment (n=6) kidneys were perfusion-fixed and examined by light and electron microscopy. Glomerular tuft volume (+140%), capillary volume (+151%) and length (+77%), mesangial volume (+115%), podocyte volume (+96%), glomerular basement membrane surface area (+107%) and filtration slit length (+85%) were all significantly greater in nephrectomized rats. The incidence of segmental glomerular sclerosis was low and variable among these rats, but was significantly higher than in controls (P=0.037). Urinary albumin excretion was elevated in the nephrectomized rats (89±72 SD mg/day vs 11±11 mg/day in control rats, P=0.01) and correlated significantly with the incidence of sclerosis (r=+0.8311, P<0.05). The relationships of the level of albuminuria and the sclerosis rate to various morphometric parameters were examined by regression analysis for the nephrectomy group. A significant negative correlation was found between albuminuria and average tuft volume (r=−0.8136) and glomerular basement membrane surface area (r=−0.8168). Both sclerosis rate and albuminuria showed negative correlations with filtration slit length (r=−0.8180 and r=−0.8598). These findings suggest that under some circumstances, glomerular hypertrophy may prevent or ameliorate the early stages of glomerular injury after subtotal nephrectomy.