MAINTENANCE OF BODY TEMPERATURE OF RESTRAINED ADRENALECTOMIZED RATS EXPOSED TO COLD: EFFECT OF ADRENAL CORTICAL HORMONES

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Abstract
To determine the role of the adrenal glands in the maintenance of colonic temperature, rats were restrained and exposed to air of 5[degree]C. Colonic temperature decreased linearly with time in the cold air; the 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 (DOCA) to adrenalectomized rats decreased CCR. Maximal decrease occurred with administration of 1.00 mg 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 given. In contrast, only the highest dose of DOCA given (4.0 mg/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 29[degree]C was returned to that of sham-operated rats when cortisone (1.00 mg or more) or ACE (0.25 ml or more) was given; 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 22.50 C; that is, the minimal colonic temperature to which adrenalectomized rats can be cooled and subsequently survive was considerably above that for normal rats (LD50 15.3[degree] C). Administration of any of the above hormones increased survival even in those doses which did not affect CCR.