Abstract

Thyroxin-treated rats are more susceptible to a standard dose of carbon tetrachloride than are control rats. Animals that ordinarily survive 20 hours after treatment, fail to live if they have previously been made thyrotoxic. Thyroxin-treated animals also exhibit liver enzyme changes 8 to 10 hours after CCl₄ administration, changes which are not demonstrable in normal CCl₄ animals sacrificed at this time. These include reduction in oxidation of mitochondrial DPN-linked dehydrogenases and oxidative phosphorylation and an increase in magnesium ATPase activity. Prior extirpation of the thyroid gland reduced the liver enzyme changes usually seen with CCl₄. Thyroxin potentiated the release of catecholamines from the adrenal, while thyroidectomy blocked this effect. Thyroxin treatment also reduced liver mitochondrial monoamine oxidase activity.

Although interrelationships between the thyroid and the adrenal are observed, their effect on lipid mobilization and deposition of the liver after CCl₄ is not clear.

The data suggest that liver enzyme changes following CCl₄ may be related to hypoxia and that potentiation or alleviation of CCl₄ effects on the liver can be produced by increasing or decreasing tissue oxygen need. The present findings are discussed in the light of the previously presented hypothesis (Calvert and Brody, 1960) that the action of CCl₄ upon liver cells is an indirect one.