Intestinal glutamine and ammonia metabolism during chronic hyperammonaemia induced by liver insufficiency

During liver insufficiency, besides portasystemic shunting, high arterial glutamine concentrations could enhance intestinal glutamine consumption and ammonia generation, thereby aggravating hyperammonaemia. To investigate this hypothesis, portal drained viscera (intestines) fluxes and jejunal tissue concentrations of ammonia and glutamine were measured in portacaval shunted rats with a ligated bile duct, portacaval shunted, and sham operated rats, seven and 14 days after surgery, and in normal unoperated controls. Effects of differences in food intake were minimised by pair feeding portacaval shunted and sham operated with portacaval shunted rats with biliary obstruction. At both time points, arterial ammonia was increased in the groups with liver insufficiency. Also, arterial glutamine concentration was raised in all operated groups compared with normal unoperated controls. At both time points, ammonia production by portal drained viscera was reduced in portacaval shunted rats with biliary obstruction, portacaval shunted, and sham operated rats compared with normal unoperated controls, and no major differences were found between these operated groups. At day 7 in all operated groups glutamine uptake by portal drained viscera was lower than in normal unoperated controls, but no major differences were found at day 14. These experiments show that ammonia generation by portal drained viscera remains unchanged in rats with chronic liver insufficiency despite alterations in arterial glutamine concentrations and intestinal glutamine uptake. The hyperammonaemia seems to be mainly determined by the portasystemic shunting.