Studies on the anti-oestrogenic and oestrogen-like action of clomiphene citrate animal experiments

In vitro effects of clomiphene citrate on human endometrium

Since cis-clomiphene citrate (CC) used for ovulation induction may affect embryo implantation during in vitro fertilization, direct effects of the drug on human endometrium were tested. Estrogenic and antiestrogenic effects were evaluated in vitro by measuring changes in prostaglandin (PG) output provoked by estradiol (E2), CC, and mixtures of E2 and CC; progestagenic effects were tested with E2 17 beta-dehydrogenase activity and glycogen accumulation as end points. In secretary endometrium, 10(-6)M CC about doubled the basal output of PGF2 alpha and PGE2; 10(-8)M E2 increased the production of these PGs 3-fold and 1.8-fold, respectively. The effects of E2 at this concentration were not diminished by the addition of CC, even at 100-fold molar excess, under conditions in which 10(-7)M progesterone or 10(-6)M 4-hydroxytamoxifen suppressed completely the action of the natural estrogen. In proliferative endometrium, 10(-8)M and 10(-6)M CC had no consistent effect on E2 17 beta-dehydrogenase activity or glycogen accumulation. These results demonstrate that, under in vitro conditions, CC can exert direct estrogenic effects on the endometrium but does not act as an antiestrogen or a progestagen.

Effect of clomiphene on the functional morphology of oviductal and uterine mucosa

The effect of clomiphene on the functional morphology of the uterine and oviductal mucosa was studied in rabbits by means of light and electron microscopy (SEM and TEM). Tissues were obtained from mature nulliparous animals receiving subcutaneous doses ranging from 0.01-10 mg/kg per day. In all cases the effects were evaluated 2 days after termination of treatment. With 2 and 10 mg, effects were studied up to 12 and 7 days, respectively. Normally appearing oviductal and endometrial tissues, corresponding to various stages of the cycle, were observed with doses up to 5 mg. However, a burst of cellular secretory activity becomes evident with the administration of higher doses. Apical protrusions or cytoplasmic portions seem to be extruded, and draw attention. These cytologic events are concentrated near gland openings in the endometrium and can be seen abundantly among cilia of oviductal cells. Other ultrastructural changes are evident as well. These histologic changes may reflect nonsynchronous cellular activities which in turn interfere with oviductal and endometrial functions before implantation.

Effect of clomiphene citrate on pituitary responsiveness to gonadotropin releasing hormone in rams and wethers

The objective of this study was to determine the effect of clomiphene citrate (clomid) on pituitary responsiveness to gonadotropin releasing hormone (GnRH) in rams and wethers. Doses of 200 mg clomid per ram and 1 mug GnRH per 50 kg body weight were used in studies on 12 rams and 4 wethers. The experimental design involved bleeding each animal at 15-minute intervals for 6.5 hours. At the end of the first hour, GnRH was injected IV. The second GnRH challenge was administered 0.5 hours after an injection of clomid or vehicle (4.5% sorbitol solution) which was given on the third hour. The relative response to clomid or vehicle was calculated as the mean increase in concentration of LH during the two-hour period after the second GnRH injection. Each treatment (clomid and vehicle) was given to all animals with a 14-day recovery period between treatment days. The relative response for the rams receiving vehicle (1.80 +/- 0.65) was greater (P < 0.05) than the response during clomid treatment (0.34 +/- 0.22). This suppression of LH response by clomid was observed in 10 of the 12 rams. In contrast to the rams, the concentrations of LH in wethers after the second GnRH injection were lower than those observed after the first GnRH injection. Similar to the rams, the relative response following clomid treatment of wethers (0.04 +/- 0.04) was less than the relative response (P > 0.05) following vehicle (0.40 +/- 0.16). The results suggest that clomid at this dosage inhibits GnRH-induced release of LH from the pituitary of rams but not of wethers.

Gonadotrophin release in ovariectomized patients. I. Suppression by clomiphene or low doses of ethinyl oestradiol

Administration of clomiphene citrate (150 mg/day) for 5 days to twenty-four ovariectomized patients and seven normal female patients evoked a significant release of FSH and LH in the normal control group and suppressed the gonadotrophin secretion in the castrated patients. A similar suppressive effect on gonadotrophin secretion was noted in eight ovariectomized patients treated for 10 days with low doses (50 microgram/day) of ethinyl oestradiol. It is suggested that in the ovariectomized hypoestrogenic patients, clomiphene acted as an oestrogen, suppressing by a negative feedback action gonadotrophin release in a way similar to ethinyl oestradiol. In the normal control group with an adequate steroid environment, clomiphene acted (probably at the hypothalamic level) as an oestrogen antagonist and stimulated gonadotrophin secretion. In view of our findings, it seems as if the ability of anovulatory patients to respond to clomiphene treatment by increased gonadotrophin secretion depends upon the absolute concentration of the compound in the different organs and by the quantitative relation of clomiphene to the endogenous oestrogens.