Influence of Age on Compensatory Renal Growth in Rats

Rats were nephrectomized (nx) or sham-operated (s) at the age of 5 days (young) or 55 days (adult). Nx and s rats from the same litters were studied at various times 5-75 days after surgery with determination of kidney weight and of renal cortical DNA and protein content. In some protocols protein and DNA content were determined in a more homogeneous population of proximal tubular cells. In s rats body weight, kidney weight, renal cortical DNA content, and protein/DNA ratio increased until at least 80 days of age. Body growth was the same in nx and s rats. In young nx rats the remnant kidney was significantly enlarged 5 days after surgery. The difference in kidney size between nx and s rats increased continuously at least until the age of 80 days. The remnant kidney was 125 +/- 9% enlarged 3 wk after nx and 175 +/- 18% enlarged 8 wk after nx. Five days after nx there was no increase in cortical DNA content but a significant increase in protein/DNA ratio. From 2 wk after nx on, the DNA content was significantly higher in nx than in s rats but the protein/DNA ratio was the same in nx and s rats. In adult nx rats, the remnant kidney was enlarged to the same extent 3 and 8 wk after surgery (130 +/- 7 and 132 +/- 8%, respectively). The increase in kidney weight 8 wk after nx was significantly smaller in adult than in young rats. The cortical DNA content and protein/DNA ratio were both moderately but significantly increased in adult rats 8 wk after nx. In conclusion this study has established age-dependent differences regarding the degree, the nature and the duration of compensatory renal growth.(ABSTRACT TRUNCATED AT 250 WORDS)