Abstract
Abstract
We investigated the role of the adrenal glands in the maintenance of serum testosterone concentrations during the 4-day estrous cycle in the rat. Animals were untreated, adrenalectomized (ADX), or sham-ADX. The operations did not alter with the length of the estrous cycle. Three to five estrous cycles after surgery, we decapitated rats for the collection of trunk blood and measured the FSH, LH, and testosterone in the serum by radioimmunoassays. Serum FSH and LH concentrations were similar in the three groups of rats during the estrous cycle except at 1000 hr of estrus when serum FSH levels were lower in the untreated rats than in the other two groups. In untreated rats, serum testosterone concentrations were lowest during estrus and highest after the onset of the preovulatory surges of FSH and LH in serum during the afternoon of proestrus. No significant differences in serum testosterone concentrations were observed between groups except that levels in the ADX rats were lower than levels in the untreated rats at 1000 and 1800 hr of diestrous day 1, and levels in the ADX rats were lower than levels in the sham-ADX rats at 0600 hr of estrus. Serum testosterone levels were undetectable in rats ovariectomized and adrenalectomized for 2 weeks. The results indicate that the adrenal glands contribute little to the maintenance of serum testosterone levels during the rat 4-day estrous cycle and that the rise in serum testosterone concentration from estrus to the afternoon of proestrus is likely the result of ovarian secretions.
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