Portal and peripheral blood ammonia concentrations in germ-free and conventional guinea pigs

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Abstract
Portal and peripheral blood ammonia concentrations were measured in germ-free and conventional guinea pigs maintained on autoclaved stock diet containing approximately 20% protein, and in animals maintained on protein-free or high (40%) protein diets a few days before study. While there was considerable variation, the portal blood ammonia concentrations of germ-free animals averaged about one-fourth those of the conventional animals. In the latter, portal ammonia concentrations increased markedly with increases in dietary protein. Smaller, but significant, increases also occurred in the germ-free animals on diets with increased protein content. In the conventional animals the peripheral blood ammonia levels increased, with increases in the portal levels. The net effect was a relatively constant peripheral/portal ammonia level ratio of about 0.1, regardless of diet. In the germ-free animals, the peripheral levels remained rather constant, with the result that this ratio decreased from approximately 0.7 in animals on the protein-free diet to about 0.2 on the 40% protein diet. Possible relationships between the peripheral and portal blood ammonia concentrations are discussed.