Early responses of glomerular filtration rate to unilateral nephrectomy

Abstract

Unilateral nephrectomy in rats was followed in 24 hr with an increase in protein, ribonucleic acid (RNA), and kidney weight equal to 6 to 10% of the prenephrectomy value. Clearance of iothalamate [C(Io)] was used to measure glomerular filtration rate (GFR). The ratio C(Io) : C(In) in rats was 0.92, but the ratio remained stable under varying experimental conditions. C(Io) measured during hypotonic expansion of extracellular fluid volume (ECFV) had increased by 21% in 24 hr, whereas there was no increase in sham operated controls in which ECFV had been expanded to the same degree. C(Io) also was increased four to five hours after nephrectomy during mannitol infusion, and 30 to 90 min after nephrectomy during either hypotonic or isotonic expansion of ECFV. These later changes were accompanied by a decrease in C(PAH). Sham operated controls did not show a change in C(Io). The findings were interpreted as indicating GFR did increase very early after nephrectomy, but the increase was not due to a change in renal blood flow and in extracellular volume. Removal of a kidney appeared to initiate activation of some regulator to increase GFR and sodium reabsorption. Whether this regulator also was essential in initiating the hypertrophy response was not examined.