MECHANISMS OF ADAPTATION TO PROTEINURIA IN ADRIAMYCIN NEPHROSIS

To evaluate the impact of urinary protein losses on whole body protein turnover (WBPT) independent of acidosis or uremia, we utilized a mode l of unilateral adriamycin nephrosis. Control rats were matched by wei ght to nephrotic rats and pair fed 22% protein chow for 14-18 days; ur inary urea nitrogen (UUN) was measured on day 12, and leucine turnover measurement was performed on the final day. Growth rates of nephrotic and pair-fed control rats did not differ during the first 2 wk of pai r feeding; thereafter, a small difference in growth could be detected. Despite an identical intake of dietary protein, UUN excretion was 29% less in the nephrotic rats (P less-than-or-equal-to 0.02). Fasting wh ole body protein synthesis and degradation did not differ between neph rotic and control rats; in contrast, leucine oxidation decreased by 21 % in nephrosis (P < 0.05). On the basis of near normal growth and norm al rates of WBPT, we conclude that nephrotic rats fed ad libitum can a dapt to the stress of continuous protein losses. A reduction in amino acid oxidation and UUN excretion were the primary mechanisms responsib le for protein conservation in experimental nephrosis.