Absence of compensatory renal hypertrophy in baboons.

1. The weights of kidneys of fifteen adolescent and forty-six adult male baboons were estimated. In contrast with what has been described in other mammals, in the majority of baboons (thirty-nine out of fifty-seven) the left kidney was heavier than the right.2. The medulla/cortex ratio was of the order of 1.8. The maximum urinary concentration, after 36 hr of food and water deprivation, averaged 1050 +/- 80 m-osmole/kg H(2)O.3. Unilateral nephrectomy was performed in twelve baboons with body weight ranging from 5 to 14 kg. In six animals, the left kidney was removed and the right kidney in the others.4. In two baboons, the left kidney was transplanted to the left iliac artery and vein, the ureters being left intact. After a few weeks, the right kidney was taken out, and the animals were kept under observation, one for a further 3 months and the other for a further 4 months.5. In none of the animals, whether after simple unilateral nephrectomy or after unilateral nephrectomy following transplant of one kidney, did the renoprival kidney show any significant enlargement.6. After unilateral nephrectomy, the health of the animals remained excellent, all the baboons increasing in body weight. The ability to concentrate urine by the renoprival kidney was not impaired.7. In contrast with what has been described in mice and rats, in unilaterally nephrectomized baboons no significant changes in the concentration of either RNA or DNA in renal cortex and medulla of the contralateral kidney were observed.8. After unilateral nephrectomy in baboons, there was a marked increase of oxygen uptake in slices from the cortex, but not from the medulla. In contrast with what had been observed in rats where the enhanced rate of oxygen uptake returned to pre-operative values, in baboons no decrease was observed, the rate of oxygen uptake remaining high during the whole period of observation.9. In the limit of time of observation (maximum 4 months) there was no evidence that unilateral nephrectomy resulted in compensatory hypertrophy of the contralateral kidney.