Impaired metabolism of methionine in severe liver diseases. II. Clinical and experimental studies on role of impaired methionine metabolism in pathogenesis of hepatic encephalopathy.

Hepatic encephalopathy in patients with severe liver disease was associated with marked elevation of either serum methionine or blood ammonia levels or with simultaneous moderate increases in both parameters. CSF methionine levels also increased in encephalopathic patients with fulminant hepatitis and liver cirrhosis. Increased influx of methionine into the brain over the theoretical values predicted from Pardridge's equation suggested that accelerated transport of serum methionine across the blood-brain barrier was observed in these cases with hepatic encephalopathy. Hepatic encephalopathy in acute carbon tetrachloride liver injury could be obtained experimentally following intraperitoneal injection of ammonium acetate in rats, which already received intragastric administration of methionine. However, similar encephalopathy could not be observed by the administration of glycine or leucine in place of methionine. These results suggest at least that methionine and ammonia act synergistically on inducing hepatic encephalopathy.