Comparison of heat and cold stress to assess thermoregulatory dysfunction in hypothyroid rats

Padnos. Comparison of heat and cold stress to assess ther-moregulatory dysfunction in hypothyroid rats. Am J Physiol Regulatory Integrative Comp Physiol 279: R2066–R2071, 2000.—How borderline impairment of thyroid function can affect thermoregulation is an important issue because of the antithyroidal properties of a many environmental toxicants. This study compared the efficacy of heat and cold stress to identify thermoregulatory deficits in rats subjected to border-line and overt hypothyroidism via subchronic exposure to propylthiouracil (PTU). After 3 wk of exposure to PTU in the drinking water (0, 2.5, 5, 10, and 25 mg/l), rats were sub-jected to a heat stress challenge (34°C for 2.5 h). After one more week of PTU treatment, the same rats were subjected to a cold stress challenge (7°C for 2.5 h). Core temperature (Tc) was monitored by radiotelemetry. Baseline Tc during th