Compensatory responses to nephron deficiency: adaptive or maladaptive?

Compensatory renal growth is a characteristic adaptation to reduced renal mass that appears to recapitulate the normal pattern of maturation of the kidney during the postnatal period. Hypertrophy of tubules (predominantly the proximal tubule) and glomeruli is accompanied by increased single nephron glomerular filtration rate and tubular reabsorption of sodium. We propose that the very factors, which contribute to the increase in growth and function of the renal tubular system, are, in the long term, the precursors to the development of hypertension in those with a nephron deficit. The increase in single nephron glomerular filtration rate is dependent on multiple factors, including reduced renal vascular resistance associated with an increased influence of nitric oxide, and a rightward shift in the tubuloglomerular feedback curve, both of which contribute to the normal maturation of renal function. The increased influence of nitric oxide appears to contribute to the reduction in tubuloglomerular feedback sensitivity and facilitate the initial increase in glomerular filtration rate. The increased single-nephron filtered load associated with nephron deficiency may promote hypertrophy of the proximal tubule and so increased reabsorption of sodium, and thus a rightward shift in the pressure natriuresis relationship. Normalization of sodium balance can then only occur at the expense of chronically increased arterial pressure. Therefore, alterations/adaptations in tubules and glomeruli in response to nephron deficiency may increase the risk of hypertension and renal disease in the long-term.