BOUND AND FREE CORTICOSTEROID IN THE PLASMA OF TWO SUBSPECIES OF DEER MICE (PEROMYSCUS MANICULATUS) AFTER EXPOSURE TO A LOW AMBIENT TEMPERATURE

Abstract

SUMMARY Paper and thin-layer chromatography were used to identify corticosterone as the only glucocorticosteroid in two subspecies of deer mice (Peromyscus maniculatus bairdii and P. m. gracilis). Free and bound corticosterone levels in plasma were determined fluorimetrically in both subspecies after exposure to cold (2 ± 0·5°) for 15 days. Initially, there was a significant rise in free and bound corticosterone in the plasma after cold exposure with return to the levels before cold exposure within 3 days in P. m. bairdii and 10 days in P. m. gracilis. The differential response to cold by P. m. gracilis is discussed in terms of a possible shift in pituitary adrenocorticotrophin (ACTH) and thyroid stimulating hormone (TSH) levels and decreased adrenal output. In general it is concluded that subspecies bairdii possesses a more sensitive pituitary-adrenal system than gracilis, and that the former has also greater ability to acclimatization to cold than the latter.