Urea cycle enzyme activities are normal and inducible by a high‐protein diet in CCl4 cirrhosis of rats

We produced moderately severe, inactive micronodular cirrhosis in rats using CCl4 and measured the urea cycle enzyme activities in liver after feeding a 15% casein diet for 1 week and again after a 60% casein diet for 1 week. There was no deficiency of any of the five urea cycle enzymes in cirrhotic livers of rats pair‐fed the 15% casein diet. Argininosuccinate synthetase and carbamyl phosphate synthetase activities were lower than in non‐pair‐fed controls by some baselines. All five enzymes in cirrhotic livers were induced 1.5‐ to 3‐fold by the high‐protein diet expressed as units per 100 gm of rat. The level of carbamyl phosphate synthetase activity was lower in the livers of rats pair‐fed the 60% casein diet than in control livers based on wet weight, collagen‐free protein and DNA, but the activities were equal expressed as units per 100 gm of rat. This example of CCl4‐induced cirrhosis in the rat does not serve as a good model for human cirrhosis, in which the urea cycle enzymes are reported to be decreased in activity.