Effects of urease-induced hyperammonemia in mouse liver. Ultrastructural, stereologic and biochemical study.

Intraperitoneal injections of urease induced a marked and sustained hyperammonemia in mice. Ultrastructural and stereologic analysis of hepatocytes from urease-treated mice showed striking changes in the mitochondria, rough and smooth endoplasmic reticulum and lysosomes. Thus, mitochondria became larger and rounder, and contained a less electron-dense matrix although their volume density remained similar to that of control cells. In addition, increases in the smooth and rough reticulum and the lysosomal compartment, were observed. Biochemical analysis of the livers from urease-treated mice revealed a significant increase in the intracellular content of water and lipids. Although the mechanism by which ammonia induces these changes remains unclear, the possible relationship between these findings and those described in the liver of humans and experimental animals in conditions of sustained hyperammonemia is discussed.