The effects of mercury ingestion on hepatic mitochondrial membranes of chicks

Cytochrome c oxidase activity was measured in livers of chicks receiving 0, 200,250 or 300 p.p.m. mercury (as HgC12) in the drinking water beginning at one week of age. In the first experiment treatment with 200 p.p.m. mercury for up to 4 weeks tended to increase the activity of cytochrome c oxidase and decrease the proportion of free (measured in untreated liver preparations) to total (measured in Triton X-100 treated liver preparations) enzyme activity as compared with controls. However, the differences, which appeared after 1 week of treatment were not always statistically significant. The fatty acid composition of mitochondrial lipids was not affected by treatment with 200 p.p.m. mercury for 4 weeks. In the second experiment, treatment with 300 p.p.m. mercury for 4 weeks resulted in significantly higher total cytochrome c oxidase specific activity and a significantly lower proportion of free to total enzyme activity as compared with controls. However, mitochondrial susceptibility to rupture by freezing and thawing was not affected. In the third experiment chicks were given 250 p.p.m. mercury in the drinking water from 1 through 9 weeks of age. The mercury-treated chicks exhibited severe tremors at 9 weeks while the controls were unaffected. Cytochome c oxidase total specific activity was significantly reduced in trembling chicks, and the proportion of free to total enzyme activity was significantly increased as was the susceptibility of isolated mitochondria to rupture by freezing and thawing. The data suggest that moderate levels of mercury administered over an 8 week period can affect adversely the integrity of mitochondrial membranes.