The effects of phenobarbital and gonadal steroids on periovulatory serum levels of luteinizing hormone and follicle-stimulating hormone in the hamster

The occurrence of ovulation and serum levels of LH and FSH (measured by radioimmunoassay) were determined in periovulatory hamsters injected with an ovulation-blocking dose of phenobarbital (Phen) combined with progesterone (P), estradiol-17beta (E2), or testosterone (T). Proestrous hamsters were treated at 1300 h with Phen plus oil, P, P plus E2, E2, T, or a second injection of Phen at 2000 h. Each treatment group was divided into 3 subgroups, each of which was serially bled 4 times at 6 h intervals beginning at 1200, 1400, and 1600 h on proestrus. Phen blocked ovulation on the next morning in all animals, while treatments that included P (1 mg) restored the normal complement of ova in 65-75% of the animals. Neither E2 (1, 10 or 50 mug) nor T (0.1 or 1 mg) overcame the Phen block of ovulation. Control hamsters had peak levels of LH between 1400 and 1800 h and a biphasic release of FSH consisting of a peak at 1600 h on proestrus, a return to basal levels at 2200 h, and a second more sustained surge between 2400 and 0800 h on the morning of estrus. Phen completely depressed the proestrous surge of both gonadotropins but only partially inhibited the second FSH elevation on the morning of estrus. In ovulatory animals, P alone or combined with 1 or 10 mug E2 restored peak LH levels at 1600 h. FSH levels on proestrus in hamsters treated with Phen plus P peaked at 1800 h, while the addition of 1 mug E2 resulted in increased FSH levels at 1600 h; peak levels in both groups were about half of control values. No proestrous increase was detected in ovulatory animals treated with P and 10 mug E2. FSH levels on estrus in hamsters injected with P alone or in combination with E2 were intermediate between those of controls and animals given Phen only. Levels of LH and FSH in animals treated with a single or double dose of Phen or Phen plus E2 or T were not different during the periovulatory period.     

Neuropeptide Y Y1-receptor stimulation is required for physiological amplification of preovulatory luteinizing hormone surges

Neuropeptide Y (NPY) has been shown to potentiate the actions of LHRH during the generation of preovulatory LH surges. It is not yet known, however, if activation of a specific subtype of NPY receptors in the anterior pituitary gland is an obligatory event in the stimulation of spontaneous LH surges. A battery of NPY receptor agonists, as well as the specific NPY Y1 receptor antagonist BIBP3226, were used to assess the role of Y1 receptors in the amplification of LH surges. In Exp 1, the potencies of a number of NPY agonists in facilitating LHRH-induced LH surges were assessed in pentobarbital (PB)-blocked, proestrous rats. The rank-ordered potencies of these compounds were determined to be PYY = [Leu31Pro34]NPY > NPY > hPP = rPP = NPY(13-36), which most closely reproduces the known rank-ordered affinties of these compounds for the Y1 receptor. In Exp 2, a Y1 subtype- specific antagonist, BIBP3226, was administered to unanesthetized, proestrous rats to assess the involvement of the Y1 receptor in the stimulation of spontaneous LH surges. The BIBP3226 compound strongly attenuated the endogenous proestrous LH surge, reducing the integrated value of LH secretion during the proestrous surge by more than 70%. In Exp 3, we assessed the ability of the Y1 receptor antagonist to block exogenous NPY effects on LHRH-induced LH surges. Treatment with BIBP3226 was found to completely prevent NPY amplification of LHRH-induced LH surges in pentobarbital-blocked, proestrous rats, thus confirming a pituitary locus of action of the drug. Taken together, these data clearly demonstrate that activation of neuropeptide Y receptors of the Y1 subtype is required for the physiological amplification of the spontaneous preovulatory LH surge in rats.     

Detection of epitopes on follicle-stimulating hormone and FSH-antiserum-induced suppression of bioactivity of follicle-stimulating hormone and luteinizing hormone

There are currently two major approaches to hormonal male contraception. One relies on testosterone (analogs) either alone or in combination with gonadotropin releasing hormone (GnRH) (analogs or immunizations), the other on immunizations against follicle-stimulating hormone (FSH). Theoretically, the latter method will suppress spermatogenesis whilst not interfering with libido. An absolute requirement is, however, that an anti-FSH vaccine does not include anti-luteinizing hormone (LH) antibodies (LH being responsible for the induction of testosterone which is necessary to maintain libido). In this report we show that when whole FSH is used for vaccination, in most cases in addition to biological activity against FSH, anti-LH activity is also induced. By systematic analysis of the antisera raised with FSH using systematic epitope scanning (PEPSCAN) we found differences between the FSH-specific and FSH-nonspecific sera. Only the FSH-specific antiserum contained antibodies that recognized amino acid sequence 37-55 on the beta-subunit in a linear manner. Because antibodies against this epitope have not been found in the cross-reactive sera this epitope forms a prime candidate for an anti-FSH contraceptive vaccine.     

Contributions of endogenous inhibin and estradiol to the regulation of follicle-stimulating hormone and luteinizing hormone secretion in the pregnant rat

To examine the contributions of endogenous inhibin and estradiol to the regulation of FSH and LH secretion in the pregnant rat, some rats were passively immunized against inhibin and/or estradiol, and others were ovariectomized, on Days 5, 10, 15, and 20 of pregnancy. Ovarian and uterine venous blood was collected separately to confirm the sources of inhibin and steroid hormones during pregnancy. Immunoreactivity of inhibin in the placenta was also examined by RIA. Levels of inhibin in ovarian venous plasma were significantly higher than those in peripheral plasma during pregnancy. No difference was observed between the levels of inhibin in uterine venous plasma and peripheral plasma. No immunoreactivity of inhibin was detected in placental homogenate from rats at Days 10, 15, and 20. FSH secretion significantly increased after immunoneutralization of inhibin during pregnancy. A marked increase in FSH secretion was noted on Days 5 and 20, and the smallest increase was observed on Day 15. Administration of estradiol antiserum (AS) alone did not induce a significant increase in FSH secretion on any day of pregnancy. However, a synergistic effect of estradiol AS and inhibin AS was observed on Day 20. On Days 5, 10, and 20, administration of inhibin AS or estradiol AS induced a significant increase in LH secretion. A synergistic effect of inhibin AS and estradiol AS on LH secretion was observed on Day 5. On Days 5 and 10, significantly high LH secretion was noted in ovariectomized rats as compared with that in rats treated with both inhibin AS and estradiol AS, indicating that other ovarian hormones such as progesterone may be involved in the suppression of LH secretion in these stages of pregnancy. These data indicate that both inhibin and estradiol, predominantly secreted from the ovary, are involved in the regulation of gonadotropin secretion during pregnancy as during the estrous cycle in the rat.     

Neuropeptide Y and enkephalin immunoreactivity in retinorecipient nuclei of the hamster pretectum and thalamus

This investigation was stimulated by the historical confusion concerning the identity of certain pretectal nuclei and by large differences reported between species with respect to which nuclei receive retinal innervation. Subcortical visual nuclei were studied using immunohistochemistry to identify retinal projections labeled following intraocular injection of cholera toxin, b fragment. In addition, neuropeptide Y (NPY) or enkephalin (ENK) immunoreactive cells and fibers were also evaluated in the retinorecipient pretectal and thalamic areas. The results confirm the established view that the retina directly innervates the nucleus of the optic tract (NOT), posterior (PPT), and olivary pretectal (OPT) nuclei. However, the retina also innervates the hamster medial (MPT) and anterior (APT; dorsal division) pretectal nuclei, results not previously reported in rodents. A commissural pretectal area (CPT) sparsely innervated by retina is also described. The data show for the first time that the posterior limitans nucleus (PLi) receives a moderately dense, direct retinal input. The PLi does not project to the cortex and appears to be a pretectal, rather than thalamic, nucleus. All retinal projections are bilateral, although predominantly contralateral. The PLi contains a moderately dense plexus of NPY- and ENK-IR fibers and terminals. However, peptidergic fibers also traverse the ATP and connect with the dorsomedial pretectium. The OPT contains ENK- and NPY-IR neurons and fibers, but is specifically identifiable by a moderately dense plexus of ENK-IR terminals. Numerous ENK-IR neurons are found in the NOT and PPT. The latter also has moderate numbers of ENK-IR fibers and terminals, but few NPY-IR neurons or fibers. The MPT contains modest numbers of ENK-IR fibers. The APT has no NPY-IR neurons or terminals, but an occasional ENK-IR neuron is seen and there is sparse ENK-IR innervation. Peptidergic innervation of the visual nuclei does not appear to be derived from the retina. The results show a set of retinally innervated, contiguous nuclei extending from the thalamic ventrolateral geniculate nucleus dorsomedially to the midbrain CPT. These nuclei plus the superior colliculus comprise a dorsal "visual shell" embracing a central core of caudal thalamus and rostral midbrain.     

Seasonal and circadian changes in the episodic release of follicle-stimulating hormone, luteinizing hormone and testosterone in rams exposed to artificial photoperiods

Six rams of an ancient breed of domesticated sheep (SOAY) were subjected to an artificial light régime of alternating periods of long days (16 h light: 8 h darkness) and short days (8 h light: 16 h darkness) which induced seasonal development and regression of the testes during a period of 36 weeks. Over 2000 blood samples were taken, and the changes in plasma levels of FSH, LH and testosterone were related to the cycle of testicular activity. During long days plasma levels of gonadotrophins became very low and the testes regressed to about 20% of their maximum size; there was a corresponding reduction in plasma testosterone levels. When the rams were returned to short days reproductive development was again stimulated after 2-3 weeks with a progressive increase in plasma FSH and LH levels and consequent hypertrophy of the testes. It took about 16 weeks of short days for testicular activity to become maximal. Blood samples collected at hourly intervals for 24 h on ten occasions during the study revealed transitory peaks in plasma FSH and LH levels indicative of episodic release. Changes in gonadotrophin secretion were modulated primarily by alterations in the frequency of episodic releas; less than 1 spike per 24 h during long days increased to a maximum of 10 spikes/24 h under short daylengths. The peaks of FSH release were of smaller amplitude than those of LH, although during periods of frequent episodic release basal levels of fsh were increased to a greater extent than those of LH. A circadian rhythm was observed in the plasma levels of FSH, LH and testosterone, which was related to increased gonadotrophin release during the dark phase of the 24 h cycle; changes in blood haematocrit were also observed. The circadian changes appeared to be correlated with the activity cycle of the animals which in turn was dictated by daylight. A possible interrelationship between the circadian cycle and the seasonal cycle is discussed.     

PACAP colocalizes with luteinizing and follicle-stimulating hormone immunoreactivities in the anterior lobe of the pituitary gland

Pituitary adenylate cyclase activating polypeptide (PACAP) and its close relative vasoactive intestinal polypeptide (VIP) were demonstrated in the anterior pituitary gland. The cells which exhibited PACAP immunoreactivity were oval or round shaped. Their distribution was similar to that of gonadotropes but the number of PACAP immunoreactive cells was less. Double labeling revealed that PACAP immunoreactivity partially colocalized with luteinizing and follicle-stimulating hormone; however, colocalization with other pituitary hormone immunoreactivities was not demonstrated. Our results suggest an autocrine or paracrine role of PACAP in the regulation of pituitary functions.     

Neuropeptide Y in hamster limbic nuclei: lack of colocalization with substance P

The medial nucleus of the amygdala (Me), bed nucleus of the stria terminalis (BNST), and medial preoptic area (MPOA) regulate copulation in the male hamster. The present study identified neuropeptide Y-immunoreactive (NPY-IR) neurons in the BNST and Me with the greatest concentration in the posteromedial and posteriordorsal subdivisions of these nuclei, respectively. NPY-IR filters are found in all three nuclei with dense plexi of NPY-IR varicosities in the most medial subdivisions. Substance P neurons are also densely concentrated in the posterior BNST and Me; however, no neurons contained both peptides. Thus, NPY and substance P neurons comprise two distinct populations within the BNST and Me of the hamster.     

Administration of antiserum against ovine follicle-stimulating hormone or ovine luteinizing hormone at pro-poestrus in the rat: effects on follicular development during the oncoming cycle

Cyclic rats received at 13.00 h on the day of pro-oestrus a single i.v. injection of one of the following antiserum preparations: AOLH (raised in rabbits against NIH-LH-S17); AOFSH (raised against NIH-FSH-S9) or pAOFSH (AOFSH preincubated with 195 mug NIH-LH-S16/ml). Rats were killed at day 1, 3 or 5 after injection, and the ovaries prepared for histological study of the antral follicles. After AOLH, ovulation and resumption of meiosis in oocytes in pre-ovulatory follicles were prevented but follicular development during the following cycle appeared undisturbed. After either AOFSH or pAOFSH, blockade of ovulation was never observed but the formation of antral follicles normally occurring between mid-pro-oestrus and mid-oestrus was postponed by about one day. The later development of antral follicles might reflect a supranormal compensatory secretion of endogenous gonadotrophin because the development does not occur in AOFSH- or pAOFSH-treated rats hypophysectomized 24 h after injection and subsequently treated with pregnant mare serum gonadotrophin in dosage approximating the amount of gonadotrophin secreted endogenously during dioestrus. The results imply (1) that the pre-ovulatory surge of LH release is not essential for follicular development during the oncoming cycle whereas (2) a surge of FSH release is required for the formation of the new cohort of antral follicles that is normally seen at the start of a new cycle.     

Site-directed mutagenesis of recombinant equine chorionic gonadotropin/luteinizing hormone: differential role of oligosaccharides in luteinizing hormone- and follicle-stimulating hormone-like activities

Equine chorionic gonadotropin (eCG) consists of highly glycosylated alpha- and beta-subunits and belongs to the glycoprotein hormone family that includes LH and FSH. eCG is a unique member of the gonadotropin family because it elicits response characteristics of both FSH and LH in other species than the horse. To determine the biological role of the N-linked oligosaccharide at Asn 56 of the alpha-subunit and O-linked oligosaccharides at the carboxyl-terminal peptide (CTP) of the beta-subunit, two mutant eCGs, in which Asn 56 of the alpha-subunit was replaced with Gln (eCG alpha 56/beta) or CTP was deleted (eCG alpha/ beta-CTP), were produced by site-directed mutagenesis and transfecting chinese hamster ovary (CHO-K1) cells. LH- and FSH-like activities were assayed in terms of testosterone production and aromatase activity in primary cultured rat Leydig cells and granulosa cells, respectively. The wild type eCG showed similar LH- and FSH-like activities to native eCG in the in vitro bioassays. The LH-like activity of eCG alpha 56/beta was greatly reduced, whereas that of eCG alpha/beta-CTP was unaffected, demonstrating that the oligosaccharide at Asn 56 of the alpha-subunit of eCG plays an indispensable role in LH-like activity. Interestingly, the FSH-like activity of eCG alpha 56/beta was increased markedly in comparison with the wild type, and that of eCG alpha/beta-CTP was also considerably increased. These data indicate that the dual activities of eCG, LH- and FSH-like activities, could be separated by removal of the N-linked oligosaccharide on the alpha-subunit Asn 56 or CTP-associated O-linked oligosaccharides.     

Leteinizing hormone and luteinizing hormone releasing hormone-like immunoreactivity in the jugular venous blood of sheep at various stages of the oestrous cycle

Luteinizing hormone and LH-RH-like immunoreactivity were measured in the jugular venous plasma of Clun Forest ewes at various stages of the oestrous cycle. Blood samples were collected through jugular venous cannulae every 2 h for at least 20 days from three ewes during the breeding season. The ewes were checked twice daily for oestrus using a vasectomized ram. Plasma LH peaks of apparent height 112-192 ng NIH-LH-S17 equivalents/ml were detected at oestrus with basal levels of 2-15 ng/ml during most of the remainder of the 17-day oestrous cycle. Peaks of LH-RH-like immunoreactivity occurred at various times of the cycle. The apparent maximal level of these peaks was 220 pg/ml compared with basal levels of less than 10 pg/ml. Further ewes (two for each group) were sampled at 4 min intervals for 12 h, (1) from onset of oestrus, (2) 36-48 h after onset of oestrus or (3) on day 10 of the oestrous cycle. In the ewes sampled at oestrus, peaks of LH-RH-like immunoreactivity were detected before, during and after the preovulatory LH peak. Those detected after the LH peak were unassociated with any further increases in the plasma LH level. In the ewes sampled 36-48 h after onset of oestrus and on day 10 of the cycle, several peaks of LH-RH-like immunoreactivity unassociated with any increases in the LH level were detected. These peaks, and those detected at oestrus, had durations of only one or two samples, and in some cases reached levels of several ng/ml compared with basal levels of less than 10 pg/ml. The significance of these results is discussed.     

Stimulatory effect of follicle-stimulating hormone on basal and luteinizing hormone-stimulated testosterone secretions by the fetal rat testis in vitro

The in vitro effect of FSH on testosterone secretion by the fetal rat testis was studied. Testes were cultured in the presence or absence of either commercial human (h) FSH (Metrodine; 200 mIU/ml) or recombinant hFSH (200 mIU/ml) for 3 days and with 100 ng/ml ovine LH during the last 4 h of culture. To avoid a stimulatory effect by the 0.4% LH that contaminates Metrodine, the cultures were performed in the presence of a monoclonal anti-hLH beta antibody and with a concentration of Metrodine that had no short term stimulatory effect on testosterone production by the fetal testes in vitro. Metrodine treatment had a positive long term effect on both basal and LH-stimulated testosterone secretion by fetal testes explanted on days 18.5, 20.5, and 22.5 postconception, which was abolished by the addition of a monoclonal anti-hFSH beta antibody. LH-free recombinant FSH also augmented basal and LH-stimulated testosterone secretion of testes explanted on days 13.5, 14.5, and 18.5 postconception. The positive effect of recombinant hFSH appeared during the second day of treatment with day 14.5 and 18.5 testes and on the third day of treatment with day 13.5 testes. As it is widely accepted that FSH receptors are exclusively localized on Sertoli cells, these results suggest that on or before day 15.5 of fetal life, 1) Sertoli cells are able to respond to FSH, 2) Sertoli cells can produce factors that are able to act on Leydig cell function, and 3) Leydig cells are sensitive to FSH-induced Sertoli cell factors. In conclusion, this study points out a potential paracrine control of fetal Leydig cell function and/or differentiation by fetal Sertoli cells as soon as fetal Leydig cells differentiate.     

Negative influence of O-linked oligosaccharides of high molecular weight equine chorionic gonadotropin on its luteinizing hormone and follicle-stimulating hormone receptor-binding activities

Three equine CG (eCG) forms with identical amino acid sequences but different mol wt and monosaccharide compositions were isolated from a crude eCG preparation and designated eCG-L (low mol wt), eCG-M (medium mol wt), and eCG-H (high mol wt). No differences in primary structure between each form and the known sequence of eCG were observed. SDS-PAGE of these preparations under reducing conditions revealed that the mol wt differences between them were due only to the different sizes of their beta-subunits. Carbohydrate compositions suggested an increase in O-glycosylation in the higher mol wt forms. N-Linked glycopeptide fragments obtained from eCG beta-subunits by endoproteinase Lys-C digestion had identical electrophoretic mobilities. Thus, the different molecular sizes of the beta-subunits were associated only with disparities in O-glycosylation of their C-terminal extension. When tested in a LH and several FSH radioligand assay systems, eCG-H proved to have significantly lower receptor-binding activities than eCG-L and eCG-M. Endo-beta-galactosidase digestion increased the FSH receptor-binding activity of all eCG forms; however, partially deglycosylated eCG-H remained the least active form. Thus, the O-linked oligosaccharides of eCG-H exert a negative influence on its receptor-binding activity.     

Differential effects of intraventricular luteinizing hormone releasing hormone (LH-RH) and norepinephrine on electrical activity of the arcuate nucleus in the proestrous rat

Effects of intraventricular infusions of LH-RH and norepinephrine (NE) on the electrical activity of the arcuate nucleus were investigated in normally cycling proestrous rats. Under urethane anesthesia, recordings were made of amplitude-discriminated multiple unit spike activity and integated multiunit activity (MUA) in parallel with cortical EEG. Control infusions of saline (2 microliter, isotonic, pH 5.5) were ineffectual, but LH-RH (0.5 microgram) induced a significant increase in both multiunit spike activity and integrated MUA. While the response appeared to be continuous, statistical analysis revealed 2 phases: a quick rise which persisted for approximately 5 min, followed 15 min later by a longer-lasting elevation in activity. The onset of the 2nd increase corresponded with the attainment of peak values of pituitary LH output. Subsequent treatment with 20 microgram NE, on the other hand, resulted in a marked depression of activity. The fact that NE depresses arcuate neuronal activity at dose levels which cause the release of LH and that LH-RH increases activity within the same population of neurons, while possibly mediating an 'ultrashort-loop' negative feedback effect, suggest that this responsive component of the arcuate nucleus, perphaps the tuberoinfundibular dopaminergic system of neurons, is inhibitory to LH release.     

On the dynamics between gonadotrophin surge-inhibiting factor and gonadotrophin releasing hormone (GnRH): role of self-priming and desensitization in the luteinizing hormone response to GnRH after follicle stimulating hormone treatment

The effects were studied of follicle stimulating hormone (FSH)-induced production of gonadotrophin surge-inhibiting factor (GnSIF) on three phases of the pituitary responsiveness to gonadotrophin releasing hormone (GnRH): the unprimed, primed and desensitized phases. Rats were injected with FSH on two occasions during the oestrous cycle. Spontaneous luteinizing hormone (LH) surges were measured as well as GnRH-induced LH surges on the day of pro-oestrus during infusions with 100-4000 pmol GnRH/rat/10 h, in phenobarbital blocked rats. The spontaneous LH surges were attenuated or completely inhibited by the FSH treatment. FSH suppresses and prolongs the unprimed LH response and delays GnRH self-priming, especially during infusions with low concentrations of GnRH. This treatment does not affect the total LH response (area under curve) to the highest concentrations of GnRH and after ovariectomy. On the other hand, this response is suppressed during infusions with the lower concentrations of GnRH. Hence, FSH, via GnSIF, delays maximal priming of the LH response to GnRH, whereas the suppression of LH release is a consequence of the GnRH-induced progressed state of desensitization. The inconsistent effects of FSH on the mid-cycle LH surges are explained as a result of the interaction between the relative strengths of GnRH and GnSIF.     

Neuropeptide Y in the human prenatal and mature gonads

The in vitro effects of a trace element preparation (béres Drops Plus, BDP) on the biosynthesis of inflammatory cytokines interleukin (IL-6, IL-1, and tumor necrosis factor-alpha (TNF-alpha) were studied in human peripheral monocytes. The production of IL-6 was studied in a glioblastoma cell line, SKMG-4, as well. The trace element preparation BDP significantly stimulated both the constitutive and the endotoxin or IL-1 induced IL-6 production in monocytes or in glial cells, respectively, but revealed no or only modest effect on IL-1 and TNF-alpha production of monocytes. Moreover, BDP was able to reduce the inhibitory effect of a synthetic corticosteroid, dexamethasone on the biosynthesis of IL-6. The positive effect of the trace element preparation on the IL-6 production of monocytes from rheumatoid arthritis (RA) patients is comparable, to that of on the monocytes from healthy individuals, and similarly to healthy individuals was negligible on the IL-1 and TNF-alpha production. The detailed analysis of the composition of the preparation suggested, that the major active component in the stimulation of IL-6 production is Zn, but for the complete effect other trace elements are also required.     

Effect of endothelin-1 in man--impact on basal and stimulated concentrations of luteinizing hormone, follicle-stimulating hormone, thyrotropin, growth hormone, corticotropin, and prolactin

The effect of endothelin-1 on basal and stimulated serum (plasma) concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyrotropin (TSH), prolactin (PRL), growth hormone (GH), and corticotropin was investigated in healthy male volunteers (n = 5). Intravenous (IV) administration of endothelin-1 (5 ng/kg/min for 15 minutes, followed by 2.5 ng/kg/min for 105 minutes) induced an increase in basal plasma concentrations of corticotropin. Serum concentrations of PRL, TSH, LH, FSH, and GH remained unchanged. The increase in serum concentrations of these pituitary hormones induced by IV administration of LH-releasing hormone ([LH-RH] 100 micrograms), thyrotropin RH ([TRH] 400 micrograms), GH-RH (100 micrograms), and corticotropin-releasing factor ([CRF] 100 micrograms) was suppressed in regard to PRL (P < .01) and GH (P < .01) and enhanced in regard to corticotropin (P < .01). Stimulated serum concentrations of LH and FSH also tended to be higher following administration of endothelin-1 (P < .05), whereas the increase in serum concentrations of TSH remained unchanged. Thus, when administered in pharmacological doses, endothelin-1 influences pituitary hormone secretion in man.     

Presence and characteristics of receptors for [D-Trp6]luteinizing hormone releasing hormone and epidermal growth factor in human ovarian cancer

This study was undertaken to establish the presence and characteristics of receptors for [D-Trp6]LH-RH on the membranes of human ovarian cancer. Specific binding of [125I, D-Trp6]LH-RH was found in 29 of 37 (78.4%) ovarian cancers and in 6 of 11 (54.5%) non-malignant human ovaries. Ligand binding was dependent on time and plasma membrane concentration in a fashion expected of a peptide hormone. Saturation, kinetic and displacement data were consistent with the presence of a highly specific, single class of non-cooperative binding site. On the basis of receptors affinity, LH-RH-receptor-positive ovarian cancers could be divided into two groups: high affinity group (Kd=2.71 +/- 0.60 nM; Bmax=0.46 +/- 0.07 pmol/mg membrane protein) comprising 55% of tumors, and low affinity group (Kd=78.0 +/- 19.6 nM; Bmax=9.44 +/- 2.68 pmol/mg membrane protein) which included 45% of tumors. LH-RH antagonist Cetrorelix showed an affinity to LH-RH receptors on ovarian cancers 14 times higher than the agonist [D-Trp6]LH-RH. Using 125I-epidermal growth factor, specific high affinity receptors were also detected in membranes from 13 of 24 (54%) ovarian cancers and 5 of 11 (45%) non-malignant ovaries. The demonstration of LH-RH receptors in human ovarian cancers provides a rationale for the use of therapeutic approaches based on LH-RH analogues in this malignancy. The probable involvement of growth factors in the development of ovarian cancers suggests the merit of trying a combined therapy based on analogs of LH-RH and somatostatin for this carcinoma.