Early responses of glomerular filtration rate to unilateral nephrectomy

Abstract

Early responses of glomerular filtration rate to unilateral nephrectomy. Unilateral nephrectomy in rats was followed in 24 hours with an increase in protein, ribonucleic acid (RNA), and kidney weight equal to 6 to 10% of the prenephrectomy value. Clearance of iothalamate (CIo) was used to measure glomerular filtration rate (GFR). The ratio CIo:CIn in rats was 0.92, but the ratio remained stable under varying experimental conditions. CIo measured during hypotonic expansion of extracellular fluid volume (ECFV) had increased by 21% in 24 hours, whereas there was no increase in sham-operated controls in which ECFV had been expanded to the same degree. CIo also was increased four to five hours after nephrectomy during mannitol infusion, and 30 to 90 minutes after nephrectomy during either hypotonic or isotonic expansion of ECFV. These later changes were accompanied by a decrease in CPAH. Sham-operated controls did not show a change in CIo. 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