Age is a determinant of the glomerular morphologic and functional responses to chronic nephron loss.

Loss of renal mass results in a compensatory increase in growth and function of remaining nephrons. Renal ablation also accelerates the expansion of mesangial matrix and the development of focal glomerulosclerosis (FGS) associated with aging. To determine whether age at the time of nephron loss influences the compensatory changes in function and the severity of subsequent glomerular lesions, immature rats (group I) and adult rats (group II) underwent right unilateral nephrectomy (Nx). Four weeks after Nx, compensatory renal growth and single nephron function showed a similar pattern in both groups. Five months after Nx, however, group I displayed significantly greater compensatory growth than group II, although both groups exhibited similar single nephron function. Moreover, group II demonstrated a significant increase in mean transcapillary hydraulic pressure difference (delta P) of approximately 5 mm Hg. Although both groups experienced accelerated expansion of mesangial matrix, significant FGS was detectable only in group I. Thus glomerular injury after Nx may result from factors other than alterations in glomerular hemodynamics.