Acclimatization to Cold in Rats: Metabolic Rates

Abstract

Exposure of clipped rats to cold air (1.5[degree]C) resulted in an increased rate of oxygen consumption in less than 3 hrs. to a level about 30% above that of undipped animals similarly exposed. This level was not maintained in unacclimatized rats, which died of hypothermia within 24 hrs. after exposure. However, in animals which had been previously acclimatized a greatly elevated metabolic rate continued for long periods. Indirect evidence is presented indicating that the increased rate of oxygen consumption of clipped over undipped animals was due, in large part, to greater muscular activity. Factors bearing on this increase are discussed.