Citrulline Levels and Urea Cycle Enzymes in Uremic Rats

Abstract

Chronically uremic rats made azotemic by surgical destruction of renal tissue, were shown to have elevated citrulline levels in plasma, liver and muscle as compared to values found in sham-operated pair-fed control animals. To assess whether these altered citrulline levels were due to increased synthesis or decreased utilization, the activities of several urea cycle enzymes were measured in liver and kidney. Activities of liver ornithine transcarbamylase and kidney arginine synthetase were lower in uremic rats than in sham-operated controls. The data suggest that the high citrulline levels found in uremia are related to a decreased conversion of citrulline to arginine.