Activities of urea-cycle enzymes in chronic liver disease

Abstract

The activities of urea-cycle enzymes were measured in liver biopsies of patients suffering from chronic-persistent hepatitis (CPH), chronic-active hepatitis (CAH) and liver cirrhosis. Most of the activities of urea-cycle enzymes did not differ in the case of CPH as compared to controls. Chronic-active hepatitis and liver cirrhosis are associated with a significant (p less than 0.05) decrease of enzyme activity as compared to normal persons. Most of the urea-cycle enzymes are significantly decreased in patients with CAH in comparison with CPH. No significant differences can be demonstrated in the case of CAH as compared to patients with complete cirrhosis. In conclusion, progression of chronic liver disease is associated with increasing alterations of enzyme activities catalyzing a liver specific metabolic pathway. The decrease of the activities of the key enzymes of the urea cycle (Carbamylphosphate-Synthetase and Arginino-succinate-Synthetase) is nearly identical both in CAH and liver cirhosis, although CAH may be a reversible disease. Therefore, marked alterations in the metabolic pathway of ammonia detoxification seem to preceed the histological manifestation of irreversible liver damage.

Metabolism of phenylalanine in liver diseases

“…In agreement with earlier studies (Maier et al 1974(Maier et al , 1979Heberer et al t980) we find in various liver diseases, especially liver cirrhosis, a decreased protein content and, unexpectedly, a normal or slightly increased DNA-content based on liver wet weight. The reason for this different development of protein-and DNA-content in liver disease is unknown.…”

“…The quantitiy of KCl-solution used was based on the finding that the human liver tissue has a water content of 65% (Heberer 1977;Heberer et al 1980;Maier et al 1979). The final proportion was img tissue per 25 !11 homogenate.…”

Neonatal intrahepatic cholestasis caused by citrin deficiency: severe hepatic dysfunction in an infant requiring liver transplantation

“…Deterioration of liver tissue results in reduction of activities of all five enzymes of the urea cycle, for example, 36% to 45% in liver cirrhosis [11]. Therefore, the reduced ASS activity in liver specimens of Case 1 is primarily caused by citrin deficiency.…”

Liver Disease and Protein Needs

“…mass. The activities of all fi ve enzymes that catalyze the steps of the urea cycle-Leo of carbamyl phosphate synthetase, ornithine carbamyltransfe rase, arginosuccinate synthetase, arginosuccinate lyase, and arginase-are decreased in cirrhosis (68,94). The most likely limiting enzymes in the urea cycle on the basis of tissue enzyme levels are carbamyl phosphate synthetase and arginosuccinate synthetase (68,159).…”