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PubMed1975

Induction of ovulation by LH and FSH in the presence of antigonadotrophic sera.

Surges of both LH and FSH are secreted on the day of proestrus in the rat; both surges are blocked by pentobarbital (PB), WHICH ALSO BLOCKS OVULATION. The purposes of the present study were (a) to see if antisera to ovine LH or FSH would prevent ovulation from endogenously secreted rat hormones; (b) to see if exogenous ovine LH or FSH alone can cause ovulation in the presence of antiserum to ovine LH or FSH, when endogenous hormone secretion is suppressed by PB. Antisera were assessed for anti-OAAD or anti-hCG augmentation activity against ovine and/or rat pituitary hormones. (a) With respect to tests against endogenously secreted hormones, antisera to LH block ovulation, but antisera to FSH do not, regardless of their potency against exogenous hormones. (b) Antisera to either ovine LH or FSH can prevent ovulation to either exogenous ovine hormone, in relation to their ability to block LH on OAAD bioassay, but not in relation to their ability to block FSH on the hCG augmentation test. However, one antiserum to FSH, which had very low anti-OAAD activity,was able to prevent ovine FSH, but not ovine LH, from causing ovulation, suggesting that not all of the ability of exogenous FSH to cause ovulation is related to intrinsic or contaminating OAAD activity. These data suggest that LH (as defined by OAAD) is the obligatory ovulating hormone in the rat. Additional data on uteirine intralumenal water in the presence of PB blockade indicate that LH, but not FSH, can induce some estrogen secretion, but that either hormone may cause some progesterone secretion.

Animals↗
PubMed1980

Preparation of a partially desialylated human chorionic gonadotrophin (hCG) and its use for induction of ovulation after ovarian stimulation with human menopausal gonadotrophin.

A method for the large scale preparation of partially desialylated human chorionic gonadotrophin suitable for human use is reported. To obtain the desired grade of desialylation and to avoid the presence of the enzyme in the modified hormone, neuraminidase coupled to Sepharose 4B was used. The preparation showed to be active in vitro (OAAD and SVW tests) and its half-life was found to be 13 min in the rat and 75 min in human beings. This desialo hCG proved to be effective in inducing ovulation in amenorrhoeic women. Among 39 induced cycles 31 ovulations and 5 pregnancies occurred.

Adult↗
PubMed1985

A possible role of clomiphene citrate in the control of pre-ovulatory LH surge during induction of ovulation.

A possible role of clomiphene citrate (clomiphene) in the control of ovulation in anovulatory women was investigated. Since a single ip administration of 5 micrograms oestradiol-17 beta (E2) to long-term ovariectomized rats did not induce LH surge, the following studies were designed to determine whether pretreatment with clomiphene followed by administration of E2 could induce LH surge in the ovariectomized rats. Changes in cytoplasmic and nuclear oestrogen receptors (ER) were also examined in the pituitaries of these animals. An ip injection of 200 micrograms clomiphene suppressed serum LH levels significantly for 72 h. The clomiphene injection rapidly caused an elevation of nuclear ER with a concomitant depletion of cytoplasmic ER level in the pituitary and the ER levels remained almost unchanged for 72 h. An administration of E2 12 or 24 h after the clomiphene injection had no significant effects on either the serum LH levels or the cytoplasmic and nuclear ER levels, compared with those induced by clomiphene alone. However, LH surge and the depletion of nuclear ER in the pituitary occurred 24 h later when E2 was injected 48 h after the clomiphene administration. The E2-induced LH release seems to be induced by a replacement of clomiphene by E2 on the nuclear receptor complex. These results suggest that clomiphene may exert actions directly on the pituitary gland to augment oestrogen-induced LH release.

Animals↗
PubMed1986

Clomiphene citrate induces pituitary GnRH receptors in ovariectomized rats: its possible role in induction of ovulation.

Since our previous studies have shown that clomiphene citrate (clomiphene) acts directly on the pituitary gland and exerts a facilitatory role on oestradiol-17 beta (E2)-induced LH surge in chronically ovariectomized rats, the effect of clomiphene on pituitary GnRH receptors was investigated. A single ip injection of either 5 micrograms E2 or 200 micrograms clomiphene did not induce LH release in adult rats ovariectomized 1-2 weeks before the injection. However, a significant increase in serum LH was noted 24 h after a single injection of E2 in the ovariectomized rats, if clomiphene was pre-injected 48 h before the E2 injection. The content of pituitary GnRH receptors in the ovariectomized rats (62 +/- 9 fmol/pituitary) remained almost unchanged until 24 h after a single injection of clomiphene but significantly increased 48 h after the injection (105 +/- 13 fmol/pituitary) without any alterations in the affinity for GnRH. To determine steroid specificity for the increase in pituitary GnRH receptors, other classes of steroids were injected in the ovariectomized rats. A single dose of E2 increased GnRH receptors, but either progesterone or 5 alpha-dihydrotestosterone failed to show any effect on the level of GnRH receptors. These results suggest that clomiphene may augment oestrogen-induced pre-ovulatory LH surge in anovulatory women, at least in part by increasing the number of pituitary GnRH receptors.

Animals↗