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Original Article

Studies of renal urea cycle enzymes. I. Renal concentrating ability and urea cycle enzymes in the rat during protein deprivation

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Pages 329-336 | Received 09 Dec 1977, Accepted 20 Dec 1978, Published online: 08 Jul 2009
 

Abstract

Activities of renal urea enzymes were studied in normally fed (21% dietary protein) rats and rats deprived of protein (6% dietary protein) for 3 weeks. Protein deprivation resulted in growth retardation and defective urine concentrating ability. Compared to rats on an optimal diet containing 21% of protein, the protein starved animals had decreased concentrations of protein and urea in serum, reduced urinary excretion of urea and decreased levels of all five urea cycle enzyme activities in the liver. In the kidney, however, protein malnutrition resulted in a significant increase in arginase specific activity from 11.5 ± 1.1 to 16.3 ± 1.5 (M ± SD) whereas the other urea cycle enzymes remained unchanged. It is postulated that this increase in renal arginase might be an early compensatory mechanism to preserve a net synthesis of urea in a situation involving arginine deficiency, thereby preserving an intact hypertonic gradient in the renal medulla.

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