Effect of L-arginine on elevated blood ammonia levels in man

Abstract

1. 1. In patients with severe liver disease the arterial blood ammonia level was usually found to be greater than the venous level. This was not observed in subjects free of liver disease. The arterial blood ammonia level was found to be a better indication of the hepatic status than the venous blood ammonia value. 2. 2. l-Arginine administered intravenously to eight subjects with advanced liver disease and hepatic encephalopathy did not produce any consistent clinical improvement or lowering of the blood ammonia. l-Arginine was similarly without significant effect when blood ammonia elevation was produced in subjects with normal liver function by exogenous (intravenous) administration of ammonium salts. These findings contrast with the marked effect of l-arginine in reducing the blood ammonia rise resulting from intravenous infusion of glycine or of an arginine-deficient l-amino acid mixture to fasted subjects. 3. 3. The significance of these findings is discussed and it is concluded that l-arginine plays an important role in preventing or reducing elevated blood ammonia levels when it acts at the site of ammonia release. After intravenous administration of certain amino acids l-arginine acts through the Krebs urea cycle to prevent ammonia formation in the liver and release into the blood. However, l-arginine administration appears to be of limited value in reducing elevated blood ammonia levels when the ammonia source is primarily exogenous, as in most instances of hepatic encephalopathy or during intravenous administration of ammonium salts.