[Interrelationship of the circadian and ovulatory rhythms of sex and gonadotropic hormone secretion in intact and neonatally androgenized female rats].

Radioimmunoassays were used to determine the LH, FSH, estradiol and progesterone content in the female rat blood in the morning (10-12 a. m.) and in the evening (5-6 p. m.). An identical circadian rhythm of the secretion of the above hormones with an increase in the level of estradiol in the morning and that of gonadotropin and progesterone in the evening was observed in intact female rats and rats neonatally androgenized with small doses of testosterone (25 Mg) and having a preserved but irregular estrous cycle. In intact female rats in the preovulatory period the circadian rhythms of the activity of different endocrine organs transformed as a result of their mutual potentiation into the preovulatory peaks of the secretion of sexual and gonadotropic hormones, and in neonatally androgenized animals, this transformation was impossible without additional stimulation because of a constantly raised level of estradiol.