Inhibition of compensatory renal growth in rats.

1. Compensatory renal hypertrophy in unilaterally nephrectomized rats was measured by estimation of dry weight, protein content, RNA and DNA changes and rate of oxygen consumption. Inulin clearances (= GFR) and water and solute excretions were estimated in animals given by stomach tube either 5 ml. water or 5 ml. 0.6% NaCl solution/100 g body wt.2. Kidneys removed when animals were unilaterally nephrectomized were homogenized in 0.25 M sucrose and fractions containing mitochondria or microsomes were obtained by centrifugation. Renal cortex and medulla were similarly treated.3. Intraperitoneal injections of microsomes and/or supernatant fluid from a kidney homogenate or from the renal cortex usually inhibited compensatory growth of the contralateral kidney and prevented any increase of its protein content.4. Injections of microsomes and/or supernatant fluid from the renal medulla had no significant effect on the rate of compensatory hypertrophy.5. After I.P. injection of microsomes and supernatant fluid from a homogenate from the renal cortex there was no rise of the RNA/DNA ratio in the contralateral kidney and the rate of oxygen uptake of its cortex decreased, while that of anaerobic glycolysis increased.6. Injections of microsomes and supernatant fluid from kidney homogenate did not affect glomerular filtration rate which increased as in control unilaterally nephrectomized rats.7. In unilaterally nephrectomized rats, injected with microsomes and supernatant fluid from a kidney homogenate, there was a decrease of osmolal clearance, in spite of the raised glomerular filtration rate. The decrease of osmolal clearance lasted for several days, and was most pronounced when the animals had been given by stomach tube 5 ml. 0.6% NaCl solution/100 g body wt.