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.
Footnotes
- Received May 31, 1961.
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