Cross-Acclimatization Between Cold and Altitude in Rats

Abstract

Rats which lived in air of 25[degree]C and were subjected for a few min. daily to 39,000 ft. simulated altitude were able, by the 14th exposure, to tolerate this condition nearly 4 times as long as they could initially. On the other hand, rats which had lived in air of 5[degree] C and were subjected daily for 14 days to the same conditions did not significantly change their tolerance to this altitude by the end of the expt. Body temp. during the brief exposures to altitude dropped about 1[degree] C in both groups under the conditions of the expt. Rats were acclimatized to 19,000 ft. altitude by continuous exposure for 2 wks. Characteristic changes were seen in hemoglobin concn. and hematocrit ratio. When immobilized and subjected to air of 5[degree] C, these rats cooled significantly more quickly than the controls. Additional expts. designed to determine the max. O2 consumption during the cooling test showed no difference between altitude and control rats, although resting O2 consumption (cc./min./kg.), under the conditions of the expt, was significantly less in the altitude group. Hence, the effect of previous continuous exposure to 19,000 ft. altitude was to decrease the tolerance to cold air. Results indicate that there is a negative cross-acclimatization both between cold and altitude, and between altitude and cold, in rats.