The effect of chronic uremia on portal and systemic ammonemia in normal and portal-strictured rats.

It is commonly assumed that the uremia occurring in cirrhotic patients leads to hepatic encephalopathy by means of hyperammonemia produced by bacterial hydrolysis of urea in the digestive tract. Therefore the effect of an increase in circulating urea on portal and systemic blood ammonia levels was investigated in normal rats and in rats with a strictured portal vein. It was shown that moderate chronic uremia, produced by subtotal nephrectomy, significantly increases both portal blood ammonia levels in normal rats and the systemic hyperammonemia resulting from portosystemic shunts in portal-strictured rats. In the latter group, despite a prolonged systemic hyperammonemia of around 400 micrograms/dl, no obvious behavioral modification could be observed, but a significant slowing of the growth rate occurred. This slowing, however, was not correlated with the systemic blood ammonia levels.