[Hyperammonemia and decrease of growth and nocturnal locomotion in rats with portal stricture and uremia]

In order to make clearer the pathogenesis of hepatic coma, the clinical tolerance of progressive levels of chronic hyperammonemia were studied in the rat. Increases of blood ammonia in the range of 200 to 600 micrograms/dl were produced within 4 weeks by stricture of the portal vein associated with progressive rises in blood urea resulting from reduction of the renal mass and/or addition of urea to the food. The portal stricture produces a collateral circulation allowing a hepatic bypass of portal blood and the ammonia level of this blood is proportional to the amount of circulating and alimentary urea hydrolyzed in the digestive tract. Only the highest hyperammonemias were associated with decreased nocturnal locomotion of the rats and decrease in the growth rate. The latter was correlated with the ammonia levels. No animal presented signs of coma. These results suggest a good cerebral tolerance by the rat of important chronic hyperammonemias which however seem to have an anorexic effect.