Toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in cold-adapted rats

The toxicity of 60 micrograms/kg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) given IP in corn oil/5% acetone was examined in male Sprague-Dawley rats adapted to 25 degrees C or 4 degrees C ambient temperature. Cold exposure significantly reduced mean time to death and tended to increase mortality. Body weight at the time of death was reduced at both ambient temperatures to about the same extent. Thus, the rate of body weight loss was about twice as fast in non-survivors at 4 degrees C than at 25 degrees C. There was a continuous decrease in feed intake of the non-survivors at 25 degrees C until death. However, no reduction in feed intake occurred in any of the rats at 4 degrees C ambient temperature. At 14 days after dosing all TCDD-dosed animals were hypothyroid in terms of T4 but essentially euthyroid in terms of T3. Oxygen consumption at 10 days after dosing was reduced to the same extent in all TCDD-dosed rats without regard to survival status. By day 20 after TCDD dosage, survivors increased their oxygen consumption at both ambient temperatures to nearly control levels whereas non-survivors were unable to do so. Body temperature of all animals remained within normal range except for the non-survivors, which showed reduced rectal temperature shortly before death.(ABSTRACT TRUNCATED AT 250 WORDS)