EFFECTS OF LONG-TERM ADRENALECTOMY ON PERIOVULATORY INCREASES IN SERUM GONADOTROPHINS AND OVULATION IN RATS

Abstract

The effects of chronic adrenalectomy on the oestrous cycle, periovulatory gonadotrophin surges in sera and ovulation in the rat were assessed. Rats which were exposed to a 14 h light : 10 h darkness lighting schedule for at least 3 weeks and those which showed at least two consecutive 4 day oestrous cycles were divided into three groups. One group (controls) was left untreated. The rest were adrenalectomized (ADX) or sham-adrenalectomized (Sham) during oestrus and then placed in a different animal room with the same lighting schedule but with the onset and end of the photoperiod delayed by 4 h. These operations did not interrupt the length of the oestrous cycles. Rats were decapitated for collection of trunk blood on the fifth pro-oestrous or oestrous day after the operation. Both Sham and ADX rats synchronized to the new lighting schedule in terms of the temporal patterns of their periovulatory surges in serum LH and FSH and the timing of ovulation. Neither adrenalectomy nor the sham-operation altered the magnitude of the pro-oestrous or oestrous increases in serum LH or FSH when compared with those in control rats. Body, uterine and ovarian weights as well as the number of ova shed were similar in the ADX and Sham groups. The results indicate that adrenal secretions are not necessary for rats to synchronize the timing of the periovulatory surges in serum LH and FSH or ovulation to a 14 h light : 10 h darkness schedule and the periovulatory surges of LH and FSH are unaltered in chronically adrenalectomized rats.