Autoregulation in rats with transplanted supernumerary kidneys.

Autoregulation of mammalian renal function is implicit in the fact that a few hours after removal of one kidney the activity of the intact nephrons in the other kidney suddenly increases, both in glomerular filtration and tubular reabsorption. There follows a slower but easily measured increase in renal mass-compensatory hypertrophy in each residual nephron. That response to a reduction of nephrons has been well studied, but the adaptation of normal renal function to additional nephrons could not be tested until microsurgical techniques made it possible to transplant one or two additional kidneys into normal rats. We report here sequential measurements of the total renal function of rats with three and four kidneys. Our results indicate that autoregulation maintains total renal function at normal levels in spite of a doubling in the number of nephrons and apparent renal mass.