Abstract
Experiments were performed to determine the role of the adrenal glands in the maintenance of colonic temperature of rats which were restrained and exposed to air at 5 °C. Colonic temperature decreased linearly with time in the cold air; hence, colonic cooling rate (CCR) was adopted as a measure of response to cold. Bilateral adrenalectomy increased CCR. Administration of cortisone acetate, adrenal cortical extract (ACE) or desoxycorticosterone acetate to adrenalectomized rats decreased CCR. Maximal decrease occurred with administration of 1.00 mgm. cortisone/rat/day or 0.25 ml. ACE/rat/day; higher doses of each hormone were less and less effective in returning CCR toward that of sham-operated rats. An adrenalectomized rat could not be rendered normal with respect to CCR no matter what dose of either ACE or cortisone was administered. In contrast, only the highest dose of DOCA administered (4.0 mgm./rat/day) significantly reduced CCR to that of sham-operated rats. The cooling test is similar to the standard growth test in that the response to administration of cortisone and ACE passes through a maximum and then declines with increasing dosage. The lower colonic temperature of adrenalectomized rats in air at 25 °C. was returned to that of sham-operated rats when cortisone (1.00 mgm. or more) or ACE (0.25 ml. or more) was administered; however, colonic temperature did not appear either to increase incrementally or to pass through a maximum with increasing doses of either hormone. DOCA had no effect on initial colonic temperature. Untreated adrenalectomized rats rarely survived lowering of colonic temperature to 22.5 °C; hence, the minimum colonic temperature to which adrenalectomized rats can be cooled and subsequently survive is considerably above that for normal rats (LD50 15.3 °C). Administration of any of the above hormones increased survival even in those doses which did not affect CCR.
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