Acclimation of adrenalectomized rats to low environmental temperature.

EVERAL authors have interpreted the S adrenal hyperactivity of normal animals exposed to low temperatures (1, 2) and the reduced cold resistance of adrenalectomized animals (3-5), as indications of the importance of the adrenal glands in the acquisition of resistance to low temperatures. However, in studies on acclimation to other types of stressing conditions (6, 7) it has been found that adrenalectomized animals, not treated with adrenal hormones, would develop a certain degree of resistance if maintained on a saline drinking solution and exposed only gradually to the stressor. The possibility that cold resistance might be developed in adrenalectomized animals under similar conditions has been considered in the present investigations. In a first series of experiments, cold resistance of normal and adrenalectomized rats with or without implanted DCA2 pellets was compared after warm or cold acclimation. In a second series, cold resistance was determined in adrenalectomized warm and cold acclimated rats that were examined, by three different methods, for evidence of accessory or regenerated adrenal tissue.