EFFECT OF COLD ON RATS CHRONICALLY EXPOSED TO MALATHION

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Abstract
Wistar rats received 4000 p.p.m. of malathion in their daily diet without showing evidence of intoxication (normal appearance, growth, food intake). When the animals were clipped and exposed to an ambient temperature of 1.5 °C they survived for a much shorter period in the cold environment than did control animals not receiving malathion. In both experimental and control groups, deaths occurred when body temperatures had dropped to about 18 °C. During the initial period in the cold environment, animals of both groups were able to increase their oxygen consumption to the same extent. There was no indication of an increased heat loss by the malathion-treated rats. It thus appeared likely that the insecticide decreased the ability of rats to produce heat continuously over a prolonged period at a high rate. The activities of cholinesterase in plasma were reduced in the malathion-treated rats but were not affected by the cold stress.