Effects of hypophysectomy and dexamethasone on rat adrenal response to microwaves

Circulating corticosterone levels were measured to compare the adrenocortical response to acute microwave exposure of normal, hypophysectomized, or sham-hypophysectomized rats. Plasma corticosterone levels in acutely hypophysectomized rats exposed to 60 mW/cm2 for 60 min were below control levels, indicating that the microwave-induced corticosterone response observed in normal, intact rats is dependent on ACTH secretion by the pituitary. In other groups of rats pretreated with dexamethasone before being exposed to microwaves for 60 min, the corticosterone response to a 50-mW/cm2 exposure was completely suppressed by doses equal to or greater than 3.2 micrograms dexamethasone/100 g body weight. However, the corticosterone response to a 70-mW/cm2 exposure was only partially suppressed by prior administration of 3.2 or 5.6 micrograms dexamethasone/100 g BW. The evidence obtained in these experiments, in conjunction with the results of other experiments previously reported, is consistent with the hypothesis that the stimulation of the adrenal axis in the microwave-exposed rat is a systemic, integrative process due to a general hyperthermia.