Pharmacology and toxicology of carbon tetrachloride in the sheep. III. Effect of cold and heat stress on toxicity and rates of elimination

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Abstract
The effect of cold and heat stress on the susceptibility of sheep to intoxication by carbon tetrachloride (CCl4) has been studied by following changes in plasma levels of isocitric dehydrogenase (ICD), glutamic oxalacetic transaminase (GOT), and bilirubin, and by other criteria. Cold stress (exposure to 4°C for 18 hr) considerably increased the toxicity of CCl4 in newly shorn sheep in medium condition but not of unshorn sheep in similar condition. The susceptibility of both shorn and unshorn sheep in poor condition was increased. Heat stress (40–41°C at 55–60% relative humidity for 12 hr) applied before, or before and after administration of CCl4 rendered the drug appreciably less toxic. This reduced toxicity was associated with increased respiration and increased elimination of CCl4 during the first 30–45 min as a result of the prior heat stress. Heat stress applied only after CCl4 administration did not reduce susceptibility. The findings confirm the suggestion from field observations that cold stress may increase the degree of intoxication of sheep by CCl4.