HYPERPLASIA PRECEDES INCREASED GLOMERULAR-FILTRATION RATE IN RAT REMNANT KIDNEY

Using 3H-thymidine (3H-T), we examined DNA synthesis in rats subjected to either urinephrectomy (UNI), five-sixths nephrectomy (R) or sham (S) surgery. Twenty-four, 48, or 72 hours later, animals were infused with 14C-inulin, PAH and 3H-T and clearances obtained. Prior to sacrifice, India ink was injected for glomerular counting. By 24 hours, glomerular filtration rate per nephron was significantly increased in UNI. However, in R, glomerular filtration rate per nephron was significantly lower than S until 72 hours. Total μg DNA per nephron was unchanged in UNI but significantly increased in R compared to S at all times. 3H-T incorporation into DNA was twice as great in UNI as in S and was over five-fold greater at 24 hours in R than in S; this marked increase persisted in R at 48 and 72 hours. Autoradiographs confirmed that DNA was synthesized predominantly by renal tubular cells and not infiltrating cells. These results indicate that hyperplasia in compensatory renal growth is related to the quantity of tissue removed and that, in the remnant kidney, DNA synthesis precedes the compensatory increase in glomerular filtration rate per nephron.