Acclimatization and Survival of Rats in the Cold: Effects of Clipping, of Adrenalectomy and of Thyroidectomy

Abstract

When 20 adult rats were completely clipped of fur and exposed to cold air of 1.5[degree] [plus or minus] 1[degree]C, all died within 3-23 hrs. (avg. 11.6 hrs.). Heavier rats lived longer than lighter ones. However, when 24 rats which had been acclimatized by living in the cold environment for 2 or more months were clipped, most (21) survived for 17 days or more; 11 were still living after 60 days. This difference is believed to consist in the ability of the acclimatized animals to maintain a greatly increased production of heat. The survival times of adrenalectomized and of thyroidectomized rats after exposure to cold were significantly lengthened by previous acclimatization. When groups of adult rats were exposed to cold 3 hrs. after adrenalectomy or after thyroidectomy (produced either surgically or by inclusion of propylthiouracil in the diet) the survival times averaged 2.4 and 7 days, respectively. In rats which had been acclimatized to cold for 2-3 mos., the survival time after adrenalectomy was 12 days (avg.); and varied from 19 to 38 days after thyroidectomy or feeding of propylthiouracil. Cortical and thyroid hormones are the agents that prolong survival.