[Reactions of the adrenal cortex and thyroid gland of hypophysectomized rats to hypothermia].

Male Wistar rats were hypophysectomized 7 days (group 1) and 4-7 weeks (group II) before exposure to hypothermia (4 degrees C for 1 1/2 h). The hypophysectomized rats from group I were devoid of both the posterior lobe and the adenohypophysis, while the rats from group II had the posterior hypophysis but not the adenohypophysis regenerated. A decreased arginine-vasopressin (AVP) blood level in group I (32%) and a very high level of AVP in group II (311%, P less than 0.05) was determined by RIA. The exposure to hypothermia did not influence the AVP plasma level. The thyroid hypofunction was revealed morphometrically in both hypophysectomized groups. Nevertheless, cooling stimulated the thyroid glands in rats of both experimental groups, like it was in the control. Thus, there is no evidence that thyroid gland reaction to hypothermia is affected by AVP. Cooling caused an increase of corticosteroid blood and adrenal cortex content in nonoperated control rats as well as in group II, but not in group I of experimental animals. Hence, it may be assumed that when the adenohypophysis is ablated, a high AVP blood level is necessary to realize the adrenal cortex response to hypothermia.