Influence of GnRH Agonist and Neural Antagonists on Stress-blockade of LH and Prolactin Surges Induced by 17 beta-estradiol in Ovariectomized Rats

In our previous study, we demonstrated that immobilization stress blocked estrogen-induced luteinizing hormone(LH) surge possibly by inhibiting the synthesis and release of gonadotropin-releasing hormone (GnRH) at the hypothalamic level and by blocking estrogen-induced prolactin (PRL) surge by increasing the synthesis of dopamine receptor at the pituitary level in ovariectomized rats. The present study was performed to determine whether immobilization stress affects pituitary LH responsiveness to GnRH, and whether endogenous opioid peptide (EOP) and dopamine systems are involved in blocking LH and PRL surges during immobilization stress. Immobilization stress was found to inhibit basal LH release and to completely abolish LH surge. However, the intravenous application of GnRH agonist completely restored immobilization-blocked LH surge and basal LH release. Treatment with naloxone did not exert any effect on immobilization-blocked LH surge but increased basal LH release during immobilization stress. Pimozide did not affect immobilization-blocked LH surge or basal LH release. Naloxone also decreased immobilization-induced basal PRL release, but had no effect on immobilization-blocked PRL surge. Immobilization-increased basal PRL levels were augmented by pimozide treatment and immobilization-blocked PRL surge was dramatically restored by pimozide. We conclude that immobilization stress does not impair pituitary LH response to GnRH, and that the immobilization stress-induced blockage of LH surge is probably not mediated by either the opioidergic or the dopaminergic system. However, immobilization-blockade of PRL surge may be partly mediated by the dopaminergic system.

Regulation of gonadotropin releasing hormone receptor mRNA expression in cultured rat granulosa cells

The homologous regulation of pituitary Gonadotropin Releasing Hormone Receptor (GnRH-R) mRNA expression by GnRH has been well demonstrated. However, the regulation of the ovarian GnRH-R is poorly understood. The present study was performed to demonstrate the presence of GnRH transcripts in addition to GnRH-R mRNA and the regulation of GnRH-R mRNA expression in the granulosa cells isolated from small antral follicles. The GnRH and GnRH-R mRNA levels were determined by a competitive reverse transcription-polymerase chain reaction (RT-PCR). The granulosa cells were obtained from immature rats implanted with diethylstilbestrol for 3 days. When GnRH transcript expression was examined in isolated granulosa cells by RT-PCR, the PCR products showed two bands. The larger band contained intronic sequences and the smaller band was a fully processed GnRH gene transcript identical to hypothalamic GnRH. This suggests that authentic GnRH gene transcripts are expressed in ovarian granulosa cells and may act on the granulosa cells in a paracrine or autocrine manner. Since GnRH action in the granulosa cells is mediated by specific GnRH-R, it is of interest to examine whether GnRH-R is synthesized in the granulosa cells. When the granulosa cells were cultured in media only, GnRH-R mRNA levels increased abruptly within 3 h and gradually decreased thereafter during the 24 h culture period. However, GnRH itself did not alter the GnRH-R mRNA expression levels in cultured granulosa cells. Interestingly, treatment with FSH decreased the GnRH-R mRNA levels in a dose-dependent manner. A time-course analysis revealed that the GnRH-R mRNA levels were significantly lower up to 9 h after FSH treatment, and returned to the basal level between 12 h-24 h. Activation of adenylate cyclase with forskolin also decreased the GnRH-R mRNA levels. It is therefore concluded that in the granulosa cells of the small antral follicles GnRH-R mRNA expression was not homologously regulated by GnRH, while FSH may negatively regulate GnRH-R mRNA expression in the granulosa cells possibly through a cAMP-protein kinase A pathway.

Effect of adenylate cyclase inhibitor and protein kinase C inhibitor on GnRH-induced LH release and LH beta subunit biosynthesis in rat anterior pituitary cells

According to our previous studies together with others, GnRH, a hypothalamic decapeptide, has been known to be a major regulator for LH release and its subunit biosynthesis in anterior pituitary gonadotropes. But the precise mechanisms by which GnRH exerts stimulatory effects on LH release and its subunit biosynthesis have not been clearly understood. In the present study we examined the effect of GnRH on protein kinase C (PKC) activity and intracellular cAMP content in cultured anterior pituitary cells of rat to clarify whether PKC or cAMP are involved in GnRH action. Moreover, we examined the effects of staurosporine (ST), a PKC inhibitor and 2',3'-dideoxyadenosine (2',3'-DDA), an adenylate cyclase inhibitor, on LH release and steady state LH beta subunit mRNA levels in cultured anterior pituitary cells of rat. PKC activity was rapidly increased within 30 min after GnRH treatment whereas intracellular cAMP level was elevated 18 h after GnRH treatment. ST significantly inhibited GnRH-induced LH release and LH beta subunit mRNA levels in a dose-dependent manner, showing an half maximal response at 50 nM ST. 2',3'-DDA inhibited GnRH-induced LH release and LH beta subunit mRNA levels in a dose-dependent manner in pituitary cells. From these results, it is suggested that GnRH stimulates LH beta subunit mRNA level as well as LH release in anterior pituitary cells and this GnRH action might be mediated by PKC activation and cAMP stimulation.

Studies on the Mechanism of Post-partum Amenorrhea: Pituitary-Ovarian Axis during Post-partum Amenorrhea in Lactating Women

The aim of this study is to evaluate pituitary-ovarian function at different postpartum periods during the lactational amenorrhea in order to understand the mechanism by which puerperal lactation is associated with a protracted period of amenorrhea and natural infertility. Ninety four lactating women and 119 lactating women with menstruation, aged between 21 and 38 years, volunteered for this study. The pituitary was relatively insensitive to LH-RH during the first 3 weeks following delivery. The recovery of FSH responsiveness to LH-RH occurred earlier than that of LH. Normal FSH response resumed in the 2nd week while the LH response, although not normal, started at the 3rd week postpartum. Pituitary responsiveness after the 5th week postpartum was similar to that occurring in normally menstruating women, except that FSH response was exagerated. Serum prolactin levels were elevated above 160 ng/ml until the 5th week postpartum and decreased to 84.2 ng/ml in the 6th week postpartum. It appears that at least one reason for anovulation during the first four weeks following delivery is the relative insensitivity of the pituitary to hypothalamic stimulation. Prolactin does not seem to modulate pituitary responsiveness to LH-RH. In order to clarify hormonal profiles during the lactational amenorrhea beyond the 5th week puerperium, serum levels of LH, FSH, prolactin, estradiol and progesterone were determined during different postpartum periods. Serum FSH and LH levels during 1-10 months postpartum were similar to basal levels seen during the normal menstrual cycle. Serum estradiol concentrations throughout 1-10 months postpartum, however, were significantly decreased as compared with the levels during the follicular phase of the normal menstrual cycle. Serum prolactin levels were elevated throughout 1-10 months postpartum in lactating amenorrhic women but decreased as the postpartum period lengthened. As compared with lactating amenorrhic women, lactating women with resumed menstruation showed a decrease in prolactin levels from 89.20 ng/ml to 51.39 ng/ml at 1-3 months, from 75.08 ng/ml to 49.99 ng/ml at 4-6 months, and from 54.73 ng/ml to 28.74ng/ml at 7-10 months postpartum. These results suggest that the apparent anovulation seen beyond 5th week postpartum during lactation was not due to pituitary insensitivity to LH-RH. Rather, prolactindependent mechanism interfering with cyclic activity may be operative during long term lactation.

Patterns of Circulating Gonadotropins (LH and FSH), Prolactin and Ovarian Steroids (Estradiol and Progesterone) during the Menstrual Cycle in Korean Women

Serum levels of LH, FSH and prolactin and plasma levels of estradiol and progesterone were measured by radioimmunoassay from 8 healthy volunteers on no medication for at least 3 months prior to study and with histories of regular menstrual cycle. The following criteria were used to define a normal menstrual cycle:1) mid-cycle LH surge, 2) luteal phase duration between 12 and 16 days, 3) plasma progesterone levels above 5 ng/m1 5-10 days after LH surge. Six of eight cycles studied were considered normal. Serum levels of LH from 6 women were fair1y constant through the cycle, except at midcycle, when a surge occurred. The rapid increase of LH secretion was during the late follicular phase with a mean peak value of 147.5 mIU/ml. Concentration of FSH started to rise after the onset of menses and decreased slight1y during the late follicular phase. FSH rose sharply at midcycle with a mean peak value reaching 36.8 mIU/ml. Following the midcycle FSH and LH surge, FSH and LH decreased sharply and remained at lower concentration during the luteal phase than during the follicular phase. Serum prolactin concentrations fluctuated throughout the menstrual cycle. There was no peak value of prolactin concomitant to the LH peak. Plasma estradiol gradually increased during the follicular phase reaching a maximum of 354.3 pg/ml prior the midcycle LH surge. Following its peak, the level of estradiol dropped sharply and started to increase from the 3rd day after LH peak, rising to 235.9 pg/ml during the midluteal peak. Plasma progesterone levels remained consistently low during the follicular phase and started to rise after the midcycle surge of LH. This rise persisted from day 5 to day 9 after the LH surge, showing a mean value of 26.1 ng/m1. Afterward, a sharp decline occurred resulting in menstruation. Two cycles studied were considered abnormal. Both cycles showed a "short luteal phase".

Carcinoembryonic Antigen in Patients with Cervical Carcinoma

The determination of carcinoembryonic antigen (CEA) in serum has been of much interest currently concomitant with the search for an immunologic diagnosis test. In this study, serum CEA values from 68 patients with histologically proved cervical carcinoma were determined by radioimmunoassay before or/and at two, intervals after radiotherapy. Fourteen patients of 68 had CEA values over 10ng per milliliter before treatment. The incidence of positive CEA values was higher in the advanced stages of disease. Three patients of five with CEA levels greater than 10ng per milliliter before treatment showed a drop of CEA levels to be1ow 10ng per milliliter seven weeks after treatment whereas two patients showed no change in CEA values at the end of radiotherapy. Two patients with palliative therapy showed no change in CEA values. The CEA test seems to be of little value for the early diagnosis and the evaluation of therapy in patients with cervical carcinoma but appears to be interesting for the surveillance of patients who have shown a drop of CEA level after therapy.

Urinary Estriol Determinations in Normal and Pathological Pregnancies

Estriol excreation was studied in 216 normal and 61 pathologic pregnancies. The 95% fiducial limits of the normal excretion of estriol, within which 95% out of 100 future determinations in normal pregnancies are expected to fall, were established. The estriol curve in normal pregnancy in this study agrees well in its general shape with those presented by previous investigators who used different chemical methods of determination. The estriol values in pathologic pregnancies with preeclampsia. intrauterine fetal death and antepartum hemorrage have been analyzed. The clinical significance of estriol determinations during pregnancy was discussed.