Effects of danazol on the pituitary-gonadal axis in male gerbils and mice

Danazol administration caused lesions in the seminiferous tubules of gerbils and mice. The seminiferous epithelium became systematically depleted of spermatogonia, spermatocytes, spermatids, and finally spermatozoa. Danazol administration did not cause damage to the epididymal cells but was followed by a significant increase (p smaller than 0.01) in the diameter of the Leydig cell nuclei. The growth of androgen-dependent organs was reversibly suppressed after treatment. Resumption of normal gonadal function in the mouse occurred 32 days after discontinuation of medication. Danazol brought about transient changes resembling those of bilateral gonadectomy in the anterior lobe of the hypophysis. Inhibition of endogenous gonadotropins occurred, reflected in the increased basophilic cell percentage.

A counter antigonadotrophic effect of melatonin in male rats

Blinding and anosmia in male rats is followed by retarded bodily development, reduced weights of the gonads and adnexa, and depressed levels of pituitary luteinizing hormone and prolactin. The effects of dual sensory deprivation are negated, for the most part, by either pinealectomy or the weekly subcutaneous implantation of melatonin (in beeswax). This is the first report that melatonin negates the antigonadotrophic influence of the rat pineal gland.

Evidence of antagonism between prolactin and gonadotrophin secretion: effect of methalibure on perphenazine-induced prolactin secretion inovariectomized rats

Perphenazine has previously been shown to stimulate prolactin secretion in intact and to a lesser degree in ovariectomized virgin female rats. The question whether the oversecretion of gonadotrophins (follicle-stimulating hormone and luteinizing hormone) occurring in ovariectomized animals interferes with the ability of the pituitary cells to secrete prolactin was investigated in sham-operated and ovariectomized rats after separate and combined treatment with methallibure (ICI-33828, a non-steroidal gonadotrophin suppressor) and perphenazine which served as a prolactin releaser. Pituitary and serum prolactin were measured simultaneously by radioimmunoassay. Serum prolactin detected at the end of 5 days' treatment with perphenazine (5 mg/kg/day, s.c.) was found to be increased (81 ng/ml) compared with controls (29 ng/ml). Similar treatment given to ovariectomized animals increased serum prolactin levels from 13·7 ng/ml to only 27 ng/ml. Although high doses of methallibure alone (20 mg/kg/day, s.c.) given to ovariectomized rats for 17 days restored prolactin secretion to the levels occurring in intact non-treated animals, a dose of 10 mg was ineffective. However, when 10 mg methallibure were given to perphenazine-treated ovariectomized rats, serum prolactin rose again to 80·1 ng/ml.

These results provide substantial evidence that, when the pituitary is secreting high amounts of gonadotrophin, its prolactin secretion is reduced and its ability to secrete prolactin after perphenazine challenge is limited. Once the gonadotrophic oversecretion is suppressed, more prolactin is secreted and the pituitary can again secrete high amounts of prolactin when challenged by perphenazine. The results show that in rats there exists an antagonism between gonadotrophin and prolactin secretion.

Differential response of ribonucleic acid polymerase in preneoplastic and neoplastic ovaries of mice following oestradiol treatment

The activity of RNA polymerase has been determined in the nuclear fraction of normal mouse ovaries, 60-day-old preneoplastic intrasplenic ovarian grafts, and ovarian tumours developed after 7 months of ovary grafting into the spleen. In preneoplastic grafts, RNA polymerase activity corresponds to that of normal ovaries, while in ovarian tumours, the enzyme value was 2-3 times higher. Oestradiol injected for 10 days, acting as depressant of the host pituitary gonadotrophic potency, decreased the enzyme level in the grafts, whereas no change was observed in similarly treated tumours. These facts indicate that hormonal mechanisms regulating the genetic nuclear expression are operating only in the 2-month-old preneoplastic ovarian cell, while autonomy from these regulating mechanisms is achieved by 7-month-old tumour cells.