Structural and functional characterisation of hFSH and hLH isoforms

Determination of Half-lives of Circulating FSH and LH Glycoforms in Women During GnRH Receptor Blockade

CONTEXT

Both FSH and LH circulate as 2 glycoforms, differing in number of glycans: low-N-glycosylated glycoforms, FSHtri and LHdi, and fully N-glycosylated glycoforms, FSHtetra and LHtri.

OBJECTIVES

To determine the half-lives of endogenous circulating gonadotropin glycoforms in women during GnRH receptor blockade.

DESIGN/PARTICIPANTS

Serum samples were collected in 8 healthy women before and up to 20 hours after administration of the NAL-GLU GnRH antagonist. Three women were in early follicular phase, 2 at mid-cycle phase, and 3 were postmenopausal.

MAIN OUTCOME MEASURES

The half-life of each glycoform was estimated by monoexponential decay for FSH (n = 8) and LH (n = 5). Data were analyzed using paired t tests.

RESULTS

Half-lives in the circulation of low-N-glycosylated glycoforms of both FSH and LH were shorter than those of the fully N-glycosylated glycoforms (mean; range, FSHtri 343; 116-686 minutes vs FSHtetra 757; 436-1038, minutes, P = 0.0003; LHdi 125, 84-198 minutes vs LHtri 164, 107-235 minutes, P = 0.004). The half-lives of low-and fully N-glycosylated forms of LH were shorter than the corresponding half-lives of FSH glycoforms, P = 0.0008.

CONCLUSIONS

For both FSH and LH, low-N-glycosylated glycoforms disappeared from the circulation faster than the fully N-glycosylated. The half-lives of low and fully N-glycosylated forms of LH were shorter than the corresponding half-lives of FSH. The estimated values for half-life in the circulation of total FSH and total LH will depend on the relative amounts of the 2 glycoforms of each hormone and their individual disappearance rates in circulation.

Low- and Fully N-Glycosylated Gonadotropins Circulating in Women With Polycystic Ovary Syndrome

Context

A preponderance of basic luteinizing hormone (LH) molecules having elevated bioactivity was detected in the circulation of women with polycystic ovary syndrome (PCOS). Subsequent studies have shown that LH and follicle-stimulating hormone (FSH) both circulate as glycoforms differing in number of glycans: low-N-glycosylated glycoforms, LHdi and FSHtri, with high in vitro bioactivity, and fully glycosylated glycoforms, LHtri and FSHtetra, with high in vivo bioactivity.

Objective

This work aims to characterize the glycosylation patterns on circulating gonadotropin glycoforms in women with PCOS.

Methods

Serum samples, collected from 8 women with PCOS were included. The concentration, sulfonation, and sialylation of each glycoform were determined and compared with values of serum samples from healthy women: 22 women at follicular phase, 16 at midcycle, and 15 after menopause.

Results

All the women with PCOS had higher LHdi serum levels compared with those in the follicular-phase group. Median LHdi and median LHtri levels were significantly elevated in PCOS women. The percentage of LHdi was increased from 37 to 49 and that of FSHtri was decreased from 41 to 33. The LHdi, LHtri, and FSHtetra glycoforms were more sialylated and both LH glycoforms less sulfonated in women with PCOS.

Conclusion

All women with PCOS had increased serum levels of LHdi, compared with those in the follicular phase. The percentage of LHdi was increased and that of FSHtri decreased in women with PCOS. The increased LHdi leads to maintenance of the abnormal early follicular development of the polycystic ovary, and the decreased FSHtri contributes to the arrested follicle growth.

Gonadotropin Glycoforms Circulating in Women Using Progestins of the Levonorgestrel Family for Contraception

Context

The progestins of the levonorgestrel family are 13-ethylgonane progestins, commonly used for contraception in women. One contraceptive effect of these progestins is inhibition of ovulation, which may be a result of changes in gonadotropin glycosylation patterns. Gonadotropin glycoforms differ in number of glycans and bioactivity: more bioactive low-N-glycosylated glycoforms, diglycosylated luteinizing hormone (LHdi) and triglycosylated follicle-stimulating hormone (FSHtri), and less bioactive fully N-glycosylated glycoforms, LHtri and FSHtetra.

Objective

Characterize the glycosylation patterns on the circulating gonadotropin glycoforms in women using 13-ethylgonane progestins for contraception.

Design, Subjects, Main Outcome Measures

Serum samples, collected from 92 healthy women using 13-ethylgonane progestins for contraception, were included. Forty women used progestin-only continuously and 52 used progestins combined with ethinylestradiol (EE) for 3 weeks followed by a hormone-free week. Concentration, sulfonation, and sialylation of each glycoform were determined and compared with follicular phase values of normal menstrual cycles.

Results

The progestin-only group had significantly increased serum levels, decreased sulfonation, and increased sialylation of LHdi. The LHdi/FSHtri ratio was increased. The progestin+EE group had significantly decreased gonadotropin glycoform concentrations and decreased sialylation of FSHtri. The progestin+EE effect on sialylation of FSHtri occurred later during the treatment cycle in contrast to the effect on FSHtri concentration.

Conclusions

The 2 different progestin treatments induced different effects on the glycan synthesis and concentrations of more bioactive low-glycosylated gonadotropins. Progestin-only treatment increased sialylation and decreased sulfonation of LHdi molecules, contributing to sustained higher levels of bioactive LHdi molecules. Progestin+EE treatment decreased sialylation of FSHtri, contributing to a shorter half-life and decreased levels of bioactive FSHtri.

Pituitary porcine FSH, and recombinant bovine and human FSH differentially affect growth and relative abundances of mRNA transcripts of preantral and early developing antral follicles in goats

Three different sources of FSH (porcine pituitary, pFSH; recombinant bovine, rbFSH; and recombinant human, rhFSH) were compared during in vitro culture of preantral and early antral follicles of goats for 18 days. Treatments were: base medium supplemented with no FSH (control), 10, 50, or 100 mIU/mL pFSH (pFSH10, pFSH50, and pFSH100, respectively), 100 ng/mL rbFSH (rbFSH), and 50 mIU/mL rhFSH (rhFSH). There were evaluations of follicle morphology, antrum formation, growth rate, estradiol production, oocyte viability and chromatin configuration, and follicle wall relative abundance of mRNA transcript for MMP-9, TIMP-2, CYP17, CYP19A1, FSHR, Insulin-R, and BAX/BCL-2 ratio. Follicle degeneration rates were similar among all treatment groups at the end of culturing. When there were treatments with pFSH, however, there was a lesser (P < 0.05) percentage of intact follicles and estradiol production, and greater (P < 0.05) extrusion rates. Furthermore, with only pFSH10 (antral follicles) and pFSH100 (preantral and antral follicles) treatments, there was a lesser (P < 0.05) follicle growth. For preantral follicles, when there was addition of pFSH10, pFSH100, and rhFSH there was lesser (P < 0.05) oocyte meiotic resumption compared to control and rbFSH treatments. For antral follicles, when there were treatments with rhFSH and pFSH10 there was greater (P = 0.08 - P < 0.05) oocyte maturation. In conclusion, the source of FSH differentially affected gene expression, as indicated by mRNA abundances, and follicular dynamics of preantral and antral follicles in vitro. Addition of FSH during the in vitro culture improved the developmental outcomes only for antral follicles.

Neuroendocrine, autocrine, and paracrine control of follicle-stimulating hormone secretion

Follicle-stimulating hormone (FSH) is a glycoprotein hormone produced by gonadotropes in the anterior pituitary that plays a central role in controlling ovarian folliculogenesis and steroidogenesis in females. Moreover, recent studies strongly suggest that FSH exerts extragonadal actions, particularly regulating bone mass and adiposity. Despite its crucial role, the mechanisms regulating FSH secretion are not completely understood. It is evident that hypothalamic, ovarian, and pituitary factors are involved in the neuroendocrine, paracrine, and autocrine regulation of FSH production. Large animal models, such as the female sheep, represent valuable research models to investigate specific aspects of FSH secretory processes. This review: (i) summarizes the role of FSH controlling reproduction and other biological processes; (ii) discusses the hypothalamic, gonadal, and pituitary regulation of FSH secretion; (iii) considers the biological relevance of the different FSH isoforms; and (iv) summarizes the distinct patterns of FSH secretion under different physiological conditions.

Development of a robust reporter gene-based assay for the bioactivity determination of recombinant human follicle stimulating hormone (rhFSH) pharmaceutical products

FSH plays a key role in the function of the reproductive system of human beings and is widely used both diagnostically and therapeutically in reproductive medicine. With the growing incidence of infertility, the demand for FSH pharmaceutical products is increasing. For this reason, the quality control process for FSH products is becoming more stringent. An accurate determination of bioactivity is crucial for the safety and efficacy of recombinant human follicle stimulating hormone (rhFSH). Up to now, in-vivo bioassay based on FSH-induced increases in rat ovarian weight has been the only method widely accepted by different pharmacopoeias. However this method has such drawbacks as the complex procedures, long assay period and high variability. Here, we established a reporter gene assay (RGA) based on the CHO-K1-FSHR-CRE-Luc cell line that stably expresses human follicle stimulating hormone receptor (hFSHR), as well as a luciferase reporter under the control of cyclic adenosine monophosphate (cAMP) response elements (CRES). Our study showed that our new assay not only has good dose-dependent responsiveness to rhFSH, but it also performs excellently in terms of specificity, precision, linearity, and simplicity compared with in-vivo rat bioassays. These results implied that this robust reporter gene assay may be a viable supplement to the animal in-vivo bioassay and may be employed in potency determination of rhFSH pharmaceutical products.

Molecular regulation of follicle-stimulating hormone synthesis, secretion and action

Follicle-stimulating hormone (FSH) plays fundamental roles in male and female fertility. FSH is a heterodimeric glycoprotein expressed by gonadotrophs in the anterior pituitary. The hormone-specific FSHβ-subunit is non-covalently associated with the common α-subunit that is also present in the luteinizing hormone (LH), another gonadotrophic hormone secreted by gonadotrophs and thyroid-stimulating hormone (TSH) secreted by thyrotrophs. Several decades of research led to the purification, structural characterization and physiological regulation of FSH in a variety of species including humans. With the advent of molecular tools, availability of immortalized gonadotroph cell lines and genetically modified mouse models, our knowledge on molecular mechanisms of FSH regulation has tremendously expanded. Several key players that regulate FSH synthesis, sorting, secretion and action in gonads and extragonadal tissues have been identified in a physiological setting. Novel post-transcriptional and post-translational regulatory mechanisms have also been identified that provide additional layers of regulation mediating FSH homeostasis. Recombinant human FSH analogs hold promise for a variety of clinical applications, whereas blocking antibodies against FSH may prove efficacious for preventing age-dependent bone loss and adiposity. It is anticipated that several exciting new discoveries uncovering all aspects of FSH biology will soon be forthcoming.

Modulation of the steroidogenic related activity according to the design of single-chain bovine FSH analogs

Single-chain (SC) gonadotropins have been genetically engineered to increase the repertoire of analogs for potential use in humans and domestic animals. The major aim of the current study was to examine the steroidogenic related activity of SC FSH analogs carrying structural differences. To address this issue, we designed and expressed three SC bovine FSH analogs in CHO cells: (i) FSHβα in which the tethered subunit domains are linked in tandem; (ii) FSHβCTPα that contains the carboxy terminal peptide (CTP) of the human choriogonadotropin (hCG) β subunit as a spacer, and (iii) FSHβboCTPα in which the linker is derived from a CTP-like sequence (boCTP) decoded from the bovine LHβ DNA. The data suggested that the secretion efficiency of these variants from the transfected cells was unaffected by the presence or absence of the CTP linker, N-glycans were attached to the analogs and the hCGβ-CTP domain in the FSHβCTPα variant was O-glycosylated. In a rat immortalized granulosa cell bioassay the potency of the three variants towards progesterone secretion varied. In immature mice, the analogs increased the ovary weight and induced StAR, Cyp11a (P450scc), Cyp17 (P450c17) and Cyp19 (P450aromatase) transcripts. However, the dose dependence and amplitude of these transcript levels differed in response to FSHβα, FSHβboCTPα and FSHβCTPα. Collectively, these data suggest that the design of the FSH analog can modulate the bioactivity in vitro and in vivo. A systematic analysis of receptor activation with ligands carrying structural differences may identify new regulatory factor/s involved in the pleiotropic FSH activity.

The global effect of follicle-stimulating hormone and tumour necrosis factor α on gene expression in cultured bovine ovarian granulosa cells

BACKGROUND

Oocytes mature in ovarian follicles surrounded by granulosa cells. During follicle growth, granulosa cells replicate and secrete hormones, particularly steroids close to ovulation. However, most follicles cease growing and undergo atresia or regression instead of ovulating. To investigate the effects of stimulatory (follicle-stimulating hormone; FSH) and inhibitory (tumour necrosis factor alpha; TNFα) factors on the granulosa cell transcriptome, bovine ovaries were obtained from a local abattoir and pools of granulosa cells were cultured in vitro for six days under defined serum-free conditions with treatments present on days 3-6. Initially dose-response experiments (n = 4) were performed to determine the optimal concentrations of FSH (0.33 ng/ml) and TNFα (10 ng/ml) to be used for the microarray experiments. For array experiments cells were cultured under control conditions, with FSH, with TNFα, or with FSH plus TNFα (n = 4 per group) and RNA was harvested for microarray analyses.

RESULTS

Statistical analysis showed primary clustering of the arrays into two groups, control/FSH and TNFα/TNFα plus FSH. The effect of TNFα on gene expression dominated that of FSH, with substantially more genes differentially regulated, and the pathways and genes regulated by TNFα being similar to those of FSH plus TNFα treatment. TNFα treatment reduced the endocrine activity of granulosa cells with reductions in expression of FST, INHA, INBA and AMH. The top-ranked canonical pathways and GO biological terms for the TNFα treatments included antigen presentation, inflammatory response and other pathways indicative of innate immune function and fibrosis. The two most significant networks also reflect this, containing molecules which are present in the canonical pathways of hepatic fibrosis/hepatic stellate cell activation and transforming growth factor β signalling, and these were up regulated. Upstream regulator analyses also predicted TNF, interferons γ and β1 and interleukin 1β.

CONCLUSIONS

In vitro, the transcriptome of granulosa cells responded minimally to FSH compared with the response to TNFα. The response to TNFα indicated an active process akin to tissue remodelling as would occur upon atresia. Additionally there was reduction in endocrine function and induction of an inflammatory response to TNFα that displays features similar to immune cells.

Macro- and Micro-heterogeneity in Pituitary and Urinary Follicle-Stimulating Hormone Glycosylation

FSH glycosylation macroheterogeneity in pituitary and urinary hFSH samples was evaluated by Western blotting. Microheterogeneity in two highly purified urinary and pituitary hFSH preparations was evaluated by nano-electrospray mass spectrometry of peptide-N-glycanase-released oligosaccharides. An age-related loss of hypo-glycosylated hFSH in individual female pituitaries was indicated by progressively reduced abundance of hFSH²¹ relative to hFSH²⁴. Urinary hFSH was evaluated as a potentially non-invasive indicator of glycoform abundance, as the only way for pituitary FSH to reach the urine is through the blood. Both highly purified and crude postmenopausal urinary hFSH preparations possessed the same amount of hFSH²¹ as postmenopausal pituitary gland FSH. Considerable microheterogeneity was encountered in both pituitary and urinary hFSH glycan populations, as 84 pituitary hFSH glycan ions were observed as compared with 68 urinary hFSH glycans. The biggest quantitative differences between the two populations were reduced abundance of bisecting GlcNAc-containing and fucosylated glycans, along with sulfated glycans in the urinary hFSH glycan population. The relative abundance of sialic acid and glycan antenna did not rationalize the retarded electrophoretic mobilities of the urinary hFSHβ²¹- and α-subunit bands relative to the corresponding pituitary hFSH bands, as the most abundant glycans in the former possessed only 2 more branches and the same sialic content as in the latter. Site-specific glycosylation information will probably be necessary.

A multicenter evaluation of immunoassays for follicle-stimulating hormone, luteinizing hormone and testosterone: concordance, imprecision and reference values

BACKGROUND

Numerous laboratories in Italy use radioimmunoassay to determine concentrations of sex hormones (FSH, LH, testosterone). A comparison of assay methods is thus an important starting point for the achievement of universally accepted reference values.

AIM

To carry out an external quality assessment for FSH, LH, and testosterone.

MATERIALS AND METHODS

Fifteen aliquots from 5 serum pools were assayed in multiple replicates by 16 Italian laboratories with 5 automated immunoassays (Abbott Architect, DiaSorin Liaison, Perkin-Elmer AutoDelfia, Roche Elecsys, Siemens Immulite 2000), and 1 radioimmunoassay (Adaltis).

RESULTS

The variance was below 12% for FSH, between 11.61% and 14.76% for LH, and between 9.57% and 12.48% for testosterone. Assay precision was good, except for Elecsys at low concentrations of FSH and for Immulite at low concentrations of LH and testosterone. ARCHITECT showed a negative bias for FSH and LH and a positive bias for testosterone; Liaison a positive bias for LH; Elecsys a positive bias for FSH and a negative bias for testosterone; Immulite a positive bias for FSH; AutoDelfia a negative bias for FSH and a positive bias for testosterone. Reference ranges at the low end varied widely, even among laboratories using the same assay.

CONCLUSIONS

The analytical performances of widely used immunoassays for FSH, LH, and testosterone show a fair to strong degree of consistency. A careful evaluation of reference ranges by clinical and laboratory experts needs to be carried out, in order to reach a consensus.

LH and hCG action on the same receptor results in quantitatively and qualitatively different intracellular signalling

Human luteinizing hormone (hLH) and chorionic gonadotropin (hCG) act on the same receptor (LHCGR) but it is not known whether they elicit the same cellular and molecular response. This study compares for the first time the activation of cell-signalling pathways and gene expression in response to hLH and hCG. Using recombinant hLH and recombinant hCG we evaluated the kinetics of cAMP production in COS-7 and hGL5 cells permanently expressing LHCGR (COS-7/LHCGR, hGL5/LHCGR), as well as cAMP, ERK1/2, AKT activation and progesterone production in primary human granulosa cells (hGLC). The expression of selected target genes was measured in the presence or absence of ERK- or AKT-pathways inhibitors. In COS-7/LHCGR cells, hCG is 5-fold more potent than hLH (cAMP ED₅₀: 107.1±14.3 pM and 530.0±51.2 pM, respectively). hLH maximal effect was significantly faster (10 minutes by hLH; 1 hour by hCG). In hGLC continuous exposure to equipotent doses of gonadotropins up to 36 hours revealed that intracellular cAMP production is oscillating and significantly higher by hCG versus hLH. Conversely, phospho-ERK1/2 and -AKT activation was more potent and sustained by hLH versus hCG. ERK1/2 and AKT inhibition removed the inhibitory effect on NRG1 (neuregulin) expression by hLH but not by hCG; ERK1/2 inhibition significantly increased hLH- but not hCG-stimulated CYP19A1 (aromatase) expression. We conclude that: i) hCG is more potent on cAMP production, while hLH is more potent on ERK and AKT activation; ii) hGLC respond to equipotent, constant hLH or hCG stimulation with a fluctuating cAMP production and progressive progesterone secretion; and iii) the expression of hLH and hCG target genes partly involves the activation of different pathways depending on the ligand. Therefore, the LHCGR is able to differentiate the activity of hLH and hCG.

Novel pathways in gonadotropin receptor signaling and biased agonism

Gonadotropins play a central role in the control of male and female reproduction. Selective agonists and antagonists of gonadotropin receptors would be of great interest for the treatment of infertility or as non steroidal contraceptive. However, to date, only native hormones are being used in assisted reproduction technologies as there is no pharmacological agent available to manipulate gonadotropin receptors. Over the last decade, there has been a growing perception of the complexity associated with gonadotropin receptors' cellular signaling. It is now clear that the Gs/cAMP/PKA pathway is not the sole mechanism that must be taken into account in order to understand these hormones' biological actions. In parallel, consistent with the emerging paradigm of biased agonism, several examples of ligand-mediated selective signaling pathway activation by gonadotropin receptors have been reported. Small molecule ligands, modulating antibodies interacting with the hormones and glycosylation variants of the native glycoproteins have all demonstrated their potential to trigger such selective signaling. Altogether, the available data and emerging concepts give rise to intriguing opportunities towards a more efficient control of reproductive function and associated disorders.

Sulfation of LH does not affect intracellular trafficking

LH and FSH are produced by the same gonadotrope cells of the anterior pituitary but differ in their mode of secretion. LH secretion is primarily episodic, or regulated, while FSH secretion is primarily basal, or constitutive. The asparagine (N)-linked oligosaccharides of LH and FSH terminate with sulfate and sialic acid, respectively. TSH also contains sulfated N-linked oligosaccharides and is secreted through the regulated pathway. It has been hypothesized that sulfate plays a role in segregating LH to the regulated pathway. Using a mouse pituitary model, we tested this hypothesis by examining the secretory fate of LH from pituitaries treated with sodium chlorate, a known inhibitor of sulfation. Here we show that mouse LH is sulfated and secreted through the regulated pathway, while FSH is secreted constitutively. LH secretion from chlorate-treated pituitaries, which showed complete inhibition of sulfation, was similar to untreated pituitaries. These data suggest that the metabolic role for sulfated N-linked oligosaccharides is not for intracellular trafficking but for the extracellular bioactivity of LH.

Single- and multi-analyte determination of gonadotropic hormones in urine by Surface Plasmon Resonance immunoassay

Single- and multi-analyte detection of two gonadotropic hormones (follicle stimulating hormone (hFSH) and luteinizing hormone (hLH)) was achieved by a Surface Plasmon Resonance (SPR) immunoassay on untreated human urine samples. Multi-analyte detection was accomplished using two alternative formats which are based in the individual or simultaneous immobilization of the hormones on the sensor surface. The lowest detection limit for both hormones in urine was found to be 1 ng mL(-1), which in international units (IU) in terms of the World Health Organization (WHO) standards represents 8 mIU mL(-1) of hLH and 14 mIU mL(-1) of hFSH, respectively. The reliability of the assay was demonstrated by intra- and inter-assay variabilities < 6%, chip-to-chip variabilities < 5%, recoveries in the range of 80-120% and stability of the sensor response through more than 100 measurements. The sensitivity of this biosensing methodology renders it in a useful technique for the diagnosis of reproductive disorders, as well as for fertility monitoring.

Effect of transient hypothyroidism during infancy on the postnatal ontogeny of luteinising hormone release in the agonadal male rhesus monkey (Macaca mulatta): implications for the timing of puberty in higher primates

The present study examined whether a transient thyroid hormone (T(4)) deficit during infancy in male monkeys would compromise the arrest of luteinising hormone (LH) secretion during the infant-juvenile transition, and/or interfere with the pubertal resurgence of LH. Animals were orchidectomized and thyroidectomized (n = 3; Tx) or sham Tx (n = 3) within 5 days of birth. T(4) replacement was initiated in two Tx monkeys at age 19 weeks to reestablish a euthyroid condition. Blood samples were drawn weekly for hormone assay. Body weight, crown-rump length, and bone age were assessed throughout the study. Within a week of Tx, plasma T(4) declined to undetectable levels and, by 6-8 weeks of age, signs of hypothyroidism were evident. Transient hypothyroidism during infancy failed to prevent either arrest of LH secretion during the infant-juvenile transition or the pubertal resurgence of LH secretion, both of which occurred at similar ages to sham Tx animals. Although body weight exhibited complete catch-up with T(4) replacement, crown-rump length and bone age did not. Thus, bone age at the time of the pubertal LH resurgence in Tx animals was less advanced than that in shams. Although Tx did not influence qualitatively the pattern of gonadotrophin secretion, LH levels during infancy and after pubertal LH resurgence were elevated in Tx monkeys. This was not associated with changes in LH pulse frequency and amplitude, but half-life (53 versus 65 min) of the slow second phase of LH clearance was greater in Tx animals. These results indicate that hypothalamic mechanisms dictating the pattern of gonadotrophin-releasing hormone release from birth to puberty are not dependent on T(4) action during infancy, and fail to support the notion that onset of puberty is causally coupled to skeletal maturation. They also indicate that LH renal clearance mechanisms may be programmed in a T(4) dependent manner during infancy.

Estrogen receptor alpha signaling pathways differentially regulate gonadotropin subunit gene expression and serum follicle-stimulating hormone in the female mouse

Estrogen, acting via estrogen receptor (ER)alpha, regulates serum gonadotropin levels and pituitary gonadotropin subunit expression. However, the cellular pathways mediating this regulation are unknown. ERalpha signals through classical estrogen response element (ERE)-dependent genomic as well as nonclassical ERE-independent genomic and nongenomic pathways. Using targeted mutagenesis in mice to disrupt ERalpha DNA binding activity, we previously demonstrated that ERE-independent signaling is sufficient to suppress serum LH levels. In this study, we examined the relative roles of ERE-dependent and -independent estrogen signaling in estrogen regulation of LH, FSH, prolactin, and activin/inhibin subunit gene expression, pituitary LH and FSH protein content, and serum FSH levels. ERE-independent signaling was not sufficient for estrogen to induce pituitary prolactin mRNA or suppress pituitary LHbeta mRNA, LH content, or serum FSH in estrogen-treated ovariectomized mice. However, ERE-independent signaling was sufficient to reduce pituitary glycoprotein hormone alpha-subunit, FSHbeta, and activin-betaB mRNA expression. Together with previous serum LH results, these findings suggest ERE-independent ERalpha signaling suppresses serum LH via reduced secretion, not synthesis. Additionally, ERE-dependent and ERE-independent ERalpha pathways may distinctly regulate steps involved in the synthesis and secretion of FSH.

Inhibin A and B in vitro bioactivities are modified by their degree of glycosylation and their affinities to betaglycan

Inhibin A and B, important regulators of normal function in tissues of the reproductive axis, are glycosylated at either Asn(268) or Asn(268) and Asn(302) in the alpha-subunit to produce 31- and 34-kDa isoforms, respectively. In this study, glycosylated isoforms of recombinant human inhibin A and B were purified from conditioned medium using immunoaffinity chromatography and reversed-phase HPLC. The masses of the purified inhibin preparations were determined by several inhibin immunoassays, and their in vitro bioactivities were based on suppression of FSH release by rat pituitary cells in culture. Based on a ratio of in vitro bioactivity to immunoactivity (B:I ratio), the monoglycosylated 31-kDa inhibin A was 5-fold more potent than the diglycosylated 34-kDa inhibin A (B:I ratio, 1.22 +/- 0.15 vs. 0.24 +/- 0.05; P < 0.001, respectively). The 31-kDa inhibin B was significantly (P < 0.001) more potent (1.75 +/- 0.29) than the 34-kDa form (1.08 +/- 0.20). Because inhibin biological activity is dependent upon interactions with the coreceptor betaglycan, the effect of inhibin glycosylation on betaglycan binding was assessed. Analogous to the pattern of in vitro bioactivity, 31-kDa inhibin A was 12-fold more active (IC(50), 0.68 nM) than the 34-kDa isoform (IC(50), 8.2 nM) at displacing [(125)I]inhibin A from COS7 cells expressing betaglycan. However, the 1.6-fold difference in bioactivity of the inhibin B isoforms was not matched by differences in their affinities for betaglycan. It is concluded that glycosylation of Asn(302) of the alpha-subunit of inhibin A and B results in a decrease in bioactivity, and the effect on inhibin A, at least, is explained by its reduced affinity to betaglycan.

Pharmacokinetic factors contribute to the inverse relationship between luteinizing hormone and body mass index in polycystic ovarian syndrome

CONTEXT

Serum LH levels decrease with increasing body mass index (BMI) in women with polycystic ovarian syndrome (PCOS).

OBJECTIVE

The objective of this study was to determine whether pharmacokinetic factors contribute to the effect of obesity on LH in PCOS. PARTICIPANTS/INTERVENTIONS/SETTING: Twenty-one women with PCOS underwent frequent blood sampling, iv administration of GnRH (75 ng/kg), and sc administration of the NAL-GLU GnRH antagonist (150 microg/kg) followed by iv recombinant human LH (rhLH; 300 IU) in the General Clinical Research Center at an academic medical center.

MAIN OUTCOME MEASURES

Pharmacokinetic parameters were estimated by modeling the LH serum concentration profiles after administration of GnRH and rhLH and related to BMI.

RESULTS

Serum levels of LH and rhLH decreased in a distinctly monoexponential fashion in all patients. The apparent biological half-life of rhLH was not influenced by BMI, nor was the total body clearance or apparent volume of distribution. However, the apparent half-life of endogenous LH was inversely related to BMI (r=-0.46; P<0.04), and the estimated total body clearance of endogenous LH was positively related to BMI (r=0.53; P<0.02).

CONCLUSION

Estimated clearance and apparent half-life of endogenous LH are influenced by BMI in women with PCOS, contributing to the inverse relationship between LH and BMI in this population. The absence of an effect of BMI on the pharmacokinetics of rhLH in these subjects suggests that the effect of obesity on clearance of endogenous LH is the result of alterations in the isoform composition of LH secreted by the pituitary.

Cumulus oophorus-associated glycodelin-C displaces sperm-bound glycodelin-A and -F and stimulates spermatozoa-zona pellucida binding

Spermatozoa have to swim through the oviduct and the cumulus oophorus before fertilization in vivo. In the oviduct, spermatozoa are exposed to glycodelin-A and -F that inhibit spermatozoa-zona pellucida binding. In this study, we determined whether these glycodelins would inhibit fertilization. The data showed that the spermatozoa without previous exposure to glycodelin-A and -F acquired glycodelin immunoreactivity during their passage through the cumulus oophorus. On the other hand, when glycodelin-A or -F-pretreated spermatozoa were exposed to the cumulus oophorus, the zona pellucida binding inhibitory activity of glycodelin-A and -F was not only removed, but the spermatozoa acquired enhanced zona pellucida binding ability. These actions of the cumulus oophorus were due to the presence of a cumulus isoform of glycodelin, designated as glycodelin-C. The cumulus cells could convert exogenous glycodelin-A and -F to glycodelin-C, which was then released into the surrounding medium. The protein core of glycodelin-C was identical to that in other glycodelin isoforms, as demonstrated by mass spectrum, peptide mapping, and affinity to anti-glycodelin antibody recognizing the protein core of glycodelin. In addition to having a smaller size and a higher isoelectric point, glycodelin-C also had lectin binding properties different from other isoforms. Glycodelin-C stimulated spermatozoazona pellucida binding in a dose-dependent manner, and it effectively displaced sperm-bound glycodelin-A and -F. In conclusion, the cumulus cells transform glycodelin-A and -F to glycodelin-C, which in turn removes the spermatozoazona binding inhibitory glycodelin isoforms and enhances the zona binding capacity of spermatozoa passing through the cumulus oophorus.

Conjugated estrogens and tibolone modify the gonadotrophin glycosylation pattern in postmenopausal women

OBJECTIVE

The purpose of this study was to evaluate the changes in the percentage of glycosylation of FSH and LH when using conjugated estrogens and tibolone as hormonal therapy (HT) in postmenopausal compared with regular menstrual cycles.

DESIGN

The study had three groups, with 10 participants in each group. The control group consisted of 10 women with normal menstrual cycles, a second group with 10 postmenopausal patients who received conjugated estrogens (Premarin 0.625 mg), and a third group had 10 patients who received tibolone (Livial 2.5 mg). All patients had hormonal determinations before and 6 months after the use of HT. Concavalin-A was used to separate the different glycosylated species of gonadotrophins, defined as unbound (UB: triantennary and bisecting oligosaccharides), weakly bound (WB: biantennary and truncated oligosaccharides), and firmly bound isoforms (FB: hybrid- and high-mannose-type oligosaccharides) in patients serum. Elusions containing the fractions with the isoforms were concentrated using Centriprep membranes (Amicon, Beverly, Mass., USA) and the different gonadotrophins isoforms were quantified by chemiluminescence using an automated system Immulite.

RESULTS

The pattern of distribution of gonadotrophins glycosylation in patients treated with conjugated estrogens and tibolone was similar to that observed in the control group with normal menstrual cycles, although with different glycosylation percentage. When the glycosylation percentages were compared for FSH, in the fraction UB the glycosylation did not have significant differences, but the fraction WB that has isoforms with high amounts of oligosaccharides showed a different percentage of glycosylation, where the recovery percentage was bigger with tibolone use (p < 0.05). The FB fraction had similar hormonal glycosylation with estrogens and tibolone use. When compared, LH glycosylation showed significant differences (p < 0.05) in the fraction UB with a bigger glycosylation degree, and in the fraction FB with a smaller glycosylation percentage, both in the tibolone group compared with conjugated estrogens use.

CONCLUSIONS

Our results show that there are different percentages of glycosylation of gonadotrophins depending on type of HT (conjugated estrogens vs tibolone), and this could be of utility in young women with ovarian problem since to know the isoform that more favors to cellular activity could help a better therapeutic.

Expression and purification of feline thyrotropin (fTSH): immunological detection and bioactivity of heterodimeric and yoked glycoproteins

The goal of this study was to express and purify recombinant feline TSH as a possible immunoassay standard or pharmaceutical agent. Previously cloned feline common glycoprotein alpha (CGA) and beta subunits were ligated into the mammalian expression vector pEAK10. The feline CGA-FLAG and beta subunits were cloned separately into the pEAK10 expression vector, and transiently co-transfected into PEAK cells. Similarly, previously cloned and sequenced yoked (single chain) fTSH (yfTSH) and the CGA-FLAG sequences were ligated into the same vector, and stable cell lines selected by puromycin resistance. Expression levels of at least 1 microg/ml were achieved for both heterodimeric and yoked fTSH forms. The glycoproteins were purified in one step using anti-FLAG immunoaffinity column chromatography to high purity. The molecular weights of feline CGA-FLAG subunit, beta subunit and yfTSH were 20.4, 17, and 45 kDa, respectively. Both heterodimeric and yoked glycoproteins were recognized with approximately 40% detection by both a commercial canine TSH immunoassay and an in-house canine TSH ELISA. The yoked glycoprotein exhibited parallelism with the heterodimeric form in the in-house ELISA, supporting their possible use as immunoassay standards. In bioactivity assays, the heterodimeric and yoked forms of fTSH were 12.5 and 3.4% as potent as pituitary source bovine TSH at displacing (125)I-bTSH and 45 and 24% as potent in stimulating adenylate cyclase activity in human TSH receptor-expressing JP09 cells. However, in addition to reduced receptor binding affinity, the recombinant glycohormones produced a reduced maximal effect at maximal concentration (E(max)) suggesting the possibility of the recombinant glycohormone constructs acting as partial agonists at the human TSH receptor.

Ovine serum and pituitary isoforms of luteinising hormone during the luteal phase

The relative abundance of the different isoforms of pituitary and circulating luteinising hormone (LH) in ewes, at different times after the administration of gonadotrophin-releasing hormone (GnRH), during the luteal phase of the oestrous cycle was investigated. Sixteen ewes on Day 9 of their cycle were divided into four groups (n = 4). The control group (T0) received saline solution; the remaining animals received 100 μg GnRH (i.m.) 30, 90 or 180 min (T30, T90 and T180, respectively) before serum and pituitary gland collection. Luteinising hormone polymorphism was analysed by chromatofocusing (pH 10.5–3.5). The LH eluted from each chromatofocusing was grouped on the basis of the following three criteria: (1) according to the pH of elution (pH ≥ 10–3.5); (2) as either a basic (pH ≥ 7.5), neutral (pH 7.4–6.5) and acidic (pH ≤ 6.4) elution of LH of serum and hypophyseal origin; and (3) on the basis of distinct isoforms, of which 10 (A–J) were identifiable in hypophyseal extracts and four (A–D) were found in the serum. In general, the most abundant forms of LH in both the pituitary and serum, at all times, were basic. However, that proportion was greater in hypophyseal extracts (84 ± 3%, 81 ± 4%, 82 ± 3% and 83 ± 2% at T0, T30, T90 and T180, respectively) than in serum (51 ± 5%, 48 ± 10% and 54 ± 6% at T30, T90 and T180, respectively). Neutral and acidic LH made up a larger proportion of the total LH in sera (neutral: 17 ± 4%, 20 ± 6% and 23 ± 3% at T30, T90 and T180, respectively; acidic: 32 ± 8%, 32 ± 11% and 23 ± 6% at T30, T90 and T180, respectively) than in the pituitary extracts (neutral: 4.0 ± 0.7%, 10 ± 4%, 7 ± 2% and 5.0 ± 0.5% at T0, T30, T90 and T180, respectively; acidic: 12 ± 3%, 11 ± 2%, 12 ± 2% and 12 ± 2% at T0, T30, T90 and T180, respectively) at all times. These data reveal that the relative composition of the LH present in the pituitary gland and the LH secreted into the circulation is different, with more neutral and acidic isoforms being secreted. The pattern of circulating LH isoforms changes between 30 and 180 min after GnRH peak induction, with a greater proportion of isoform C (eluting between pH 7.0 and 6.5) at T180 compared with T30 and T90.

A Reference Preparation of Buffalo Pituitary Follicle Stimulating Hormone using Lectin Affinity Chromatography

An improved and cost effective method to isolate FSH from buffalo pituitary glands is described here. The buFSH activity was monitored throughout by a highly sensitive heterologous radioimmunoassay (sensitivity 0.2 ng oFSH/mL) and the in vivo biological activity of the final preparation was also established. A biologically active buFSH-enriched preparation with a moderate recovery (42%) was obtained. The yield of the final buFSH-enriched preparation was 26.5 mg/kg of buffalo pituitary gland. In SDS-PAGE, the purified buFSH resolved as a heterodimer of 30 kDa molecular size, with a 21 kDa presumptive alpha-subunit. This preparation was also characterized in terms of biological and some of its physicochemical properties. A high-titer antiserum to buFSH was also raised in rabbit using this preparation. The reagents generated, buFSH and buFSH-specific polyclonal antisera, have possible diagnostic and therapeutic usage for improvement of reproductive health of water buffaloes.

Antinociceptive structure-activity studies with enkephalin-based opioid glycopeptides

Development of opioid peptides as therapeutic agents has historically been limited due to pharmacokinetic issues including stability and blood-brain barrier (BBB) permeability. Glycosylation of opioid peptides can increase peptide serum stability and BBB penetration. To further define the requirements for optimizing in vivo antinociceptive potency following intravenous administration, we synthesized a series of enkephalin-based glycopeptides using solid phase 9-fluorenylmethyloxy carbamate methods. The compounds differed in the sixth and subsequent amino acid residues (Ser or Thr) and in the attached carbohydrate moiety. In vitro binding and functional smooth muscle bioassays indicated that the addition of mono- or disaccharides did not significantly affect the opioid receptor affinity or agonist activity of the glycopeptides compared with their unglycosylated parent peptides. All of the glycopeptides tested produced potent antinociceptive effects in male ICR mice following intracerebroventricular injection in the 55 degrees C tail-flick test. The calculated A(50) values for the Ser/Thr and monosaccharide combinations were all very similar with values ranging from 0.02 to 0.09 nmol. Selected compounds were administered to mice intravenously and tested for antinociception to indirectly assess serum stability and BBB penetration. All compounds tested produced full antinociceptive effects with calculated A (50) values ranging from 2.2 to 46.4 micromol/kg with the disaccharides having potencies that equaled or exceeded that of morphine on a micromoles per kilogram basis. Substitution of a trisaccharide or bis- and tris-monosaccharides resulted in a decrease in antinociceptive potency. These results provide additional support for the utility of glycosylation to increase central nervous system bioavailability of small peptides and compliment our ongoing stability and blood-brain barrier penetration studies.

Luteinizing hormone estimation

Luteinizing hormone (LH) is an important hormone of the reproductive system, which has found application in diagnosis and therapeutic medicine. It plays a vital role in the development and functioning of the reproductive system. Determination of LH concentration is important for detection of dysfunction of the pituitary-ovarian axis, diagnosis of reproductive disorders, monitoring of antifertility programmes and in therapeutic preparations. On the basis of heterogeneity and various biological effects served by the hormone, different assay systems have been developed for its estimation. Initially, LH was quantified on the basis of in vivo and in vitro endocrine activity. However, with the advancement in biotechnology, various immunoassays have been designed for performing most of the physiological and clinical studies on serum LH. The immunoassays offer improvement in sensitivity, precision and convenience over bioassays. However, these immunoassays have their own limitations and results obtained in different laboratories are often not comparable. This review makes an attempt to enumerate and compare various assay methods used in the serum LH measurement in varied clinical conditions.

Impact of carbohydrate heterogeneity in function of follicle-stimulating hormone: studies derived from in vitro and in vivo models

Carbohydrates attached to the protein core of glycoprotein hormones influence a number of intracellular and extracellular processes. As with other members of the glycoprotein hormone family, FSH is produced and released as an array of isoforms that differ from each other in the structure of their oligosaccharide attachments. In this review, we discuss how carbohydrate heterogeneity can impact on FSH action in different in vitro and in vivo systems. We present evidence for diverse effects of distinct charge isoforms at the target cell level, including differential and unique effects on various end responses, and discuss how the use of multiple cell-type assays has allowed identification of some specific effects of FSH isoforms on different cell populations and follicle compartments as well as oocyte maturation. Finally, we discuss recent information on the ability of naturally occurring and laboratory manufactured FSH isoforms to evoke particular effects on granulosa cell function and ovarian follicular maturation in vivo. Such studies have provided evidence that the type(s) of FSH signal delivered may in fact regulate distinct biological outcomes irrespective or in addition to outcomes dictated solely by clearance rate differences.

A pharmacokinetic and endocrine comparison of recombinant follicle-stimulating hormone and human menopausal gonadotrophin in polycystic ovary syndrome

Elevated LH concentrations are frequently encountered in patients with polycystic ovary syndrome (PCOS) and increased LH (either endogenous or superimposed through the use of HMG) may have detrimental effects on reproductive function. In spite of this, FSH-only products and HMG have been used indiscriminately for ovulation induction - on the basis that the administration of HMG to patients with PCOS, who are not receiving GnRH agonists, does not result in significant increases in serum LH concentrations as judged by daily single blood samples. However, both endogenous and exogenous LH have a relatively short terminal half-life and studies have reported normal serum LH, but abnormal urinary LH and emphasized that early morning urinary measurements are more informative than those in serum because they reflect nocturnal LH secretion. Therefore, the present study was undertaken to perform a pharmacokinetic and endocrine comparison of recombinant human FSH and HMG in PCOS patients including LH measurements in the urine. Five PCOS patients receiving s.c. recombinant human FSH (rhFSH) and five PCOS patients receiving i.m. HMG for ovulation induction according to a chronic low-dose step-up regimen underwent blood and urine sampling at the following study points: Point 0 was the day of HCG injection; Points 1 to 5 corresponded to days HCG -1 to -2; -3 to -4; -5 to -6; -7 to -8; and -9 to -10; respectively. Serum hormone measurements included oestradiol, FSH, LH, progesterone, inhibin A, androstenedione, testosterone, and free testosterone index. FSH and LH were also measured daily in 8-h urine samples reflecting overnight renal urine secretion. Hormone concentrations calculated as the area under the curve showed that both FSH and LH concentrations in urine were significantly higher in HMG group than in group rhFSH. It is concluded that both LH and FSH concentrations significantly accumulate in the urine of PCOS patients receiving HMG for ovulation induction in a chronic low-dose protocol as compared with rhFSH treatment.

Molecular, structural, and cellular biology of follitropin and follitropin receptor

Follitropin and the follitropin receptor are essential for normal gamete development in males and females. This review discusses the molecular genetics and structural and cellular biology of the follitropin/follitropin receptor system. Emphasis is placed on the human molecules when possible. The structure and regulation of the genes for the follitropin beta subunit and the follitropin receptor is discussed. Control of systemic and cellular protein levels is explained. The structural biology of each protein is described, including protein structure, motifs, and activity relationships. Finally, the follitropin/follitropin receptor signal transduction system is discussed.

Assessment of the in vitro and in vivo biological activities of the human follicle-stimulating isohormones

Gonadotropins are synthesized and released in different molecular forms. In this article, we present evidence that the glycosylation variants of human pituitary FSH exhibit differential and divergent effects at the target cell level and that less sialylated, short-lived variants may exert significant effects in in vivo conditions. Less acidic/sialylated glycoforms (elution pH value 6.60-4.60 as disclosed by high resolution chromatofocusing of anterior glycoprotein extracts), induced higher cAMP release, estrogen production and tissue-type plasminogen activator (tPA) enzyme activity as well as cytochrome P450 aromatase and tPA mRNA expression in cultured rat granulosa cells than the more acidic analogs (pH<4.76). By contrast, the more acidic/sialylated glycoforms induced higher alpha-inhibin subunit mRNA expression than their less acidic counterparts. In cumulus enclosed oocytes isolated from mice ovaries, addition of less acidic isoforms induced resumption of meiosis more efficiently than the more acidic analogs. Interestingly, the least acidic isoform (pH>7.10) behave as a strong antagonist of several FSH-mediated effects. Assessment of the in vivo effects of the isoforms on granulosa cell proliferation in follicles from immature rats, revealed that short-lived isoforms were equally or even more efficient than their more acidic counterparts in maintaining granulosa cell proliferation when administered immediately after hypophysectomy. These results show that the naturally occurring human FSH isoforms may exhibit differential or even unique effects at the target cell level and that factors other than the metabolic clearance rate of the molecule (including receptor-binding affinity and capability of the ligand to activate its receptor and trigger intracellular signaling) also play an important role in determining the net in vivo effects of a particular FSH variant.

Endocrine regulation of gonadotropin glycosylation

The pituitary gonadotropins--luteinizing hormone and follicle-stimulating hormone--as well as the placental choriogonadotropin belong to the family of glycoprotein hormones. These structurally related hormones, which regulate several major reproductive functions of the body, are heterodimers consisting of a common alpha-subunit noncovalently bound to a beta-subunit. The N- and O-linked oligosaccharide chains of these gonadotropins play an important role in intracellular folding, assembly, secretion, metabolic clearance, and biological activity of the hormone. Gonadotropin glycosylation is a highly complex process; within the gonadotropes it is modulated by a variety of extrapituitary factors of hypothalamic and gonadal origin. In particular, estrogens and androgens appear to regulate terminal sialylation and/or sulfation of the oligosaccharide attachments and hence some functional properties of the gonadotropin molecule determined by these residues, i.e., metabolic clearance and in vivo biopotency. Through these extrapituitary inputs, the anterior pituitary may not only regulate the quantity but also the quality of the gonadotropin signal delivered to the gonads in a given physiologic or pathologic condition.

Characterization of human FSH isoforms reveals a nonglycosylated beta-subunit in addition to the conventional glycosylated beta-subunit

Human FSH consists of a mixture of isoforms that can be separated on the basis of differences in negative charge conferred by variations in the numbers of sialic acid residues that terminate oligosaccharide branches. Western analysis of human FSH isoforms separated by chromatofocusing revealed the presence of two human FSHbeta isoforms that differed in size. A low mol wt human FSHbeta isoform was associated with all FSH isoform fractions. A high mol wt human FSHbeta isoform was associated with the more acidic fractions and increased in relative abundance as the pI decreased. Characterization of representative human FSHbeta isoforms by mass spectrometry and automated Edman degradation revealed a low mol wt isoform that was not glycosylated. A high mol wt isoform was N-glycosylated at Asn residues 7 and 24. These results indicate that pituitary human FSH consists of two classes of molecules: those that possess a nonglycosylated beta-subunit and those that possess a glycosylated beta-subunit. Glycoprotein hormones are known to be elliptical molecules, and the beta-subunit oligosaccharides project outward from the short diameter, thereby increasing it. It is interesting to speculate that this change in shape might affect ultrafiltration rates, leading to differences in delivery rates to target tissues and elimination by filtration in the kidney.

Is there any physiological role for gonadotrophin oligosaccharide heterogeneity in humans? I. Gondatrophins are synthesized and released in multiple molecular forms. A matter of fact

Carbohydrates attached to the protein core of all glycoprotein hormones play an essential role in the function of the molecule, influencing a number of intracellular and extracellular processes. As with other members of the glycoprotein hormone family, pituitary gonadotrophins are not produced as single or unique molecules but rather as arrays of isoforms that differ from each other mainly in the structure of their oligosaccharide attachments. In both experimental animals and in humans, the abundance of the different isoforms varies depending on the endocrine status of the donor present at the time of collection of the tissue or sample. Conditions characterized by an oestrogen-enriched hormonal milieu (eg. the preovulatory phase of the menstrual cycle) promote the formation and secretion of variants with relatively low sialic acid and/or sulphate content, whereas physiological deficiency of this sex steroid (as in the postmenopause) favours the production of highly sialylated, long-lived gonadotrophin variants. When tested individually, less sialylated isoforms exhibit higher receptor-binding and in-vitro biological activity but shorter plasma half-life than their more sialylated counterparts. Both the hormonal regulation and the functional differences among the naturally occurring isoforms strongly suggest that gonadotrophin heterogeneity represents a distinctly different mechanism through which the pituitary gland may regulate the intensity and duration of the gonadotrophic stimulus. Nevertheless, whereas the existence of the alternatively glycosylated variants of gonadotrophins in both the pituitary and in serum is currently without doubt, the physiological role of this phenomenon is still a controversial issue and a matter of debate.

Molecular architecture and biorecognition processes of the cystine knot protein superfamily: part I. The glycoprotein hormones

In this review article, the reader is introduced to recent advances in our knowledge on a subset of the cystine knot superfamily of homo- and hetero-dimeric proteins, from the perspective of the endocrine glycoprotein hormone family of proteins: follitropin (FSH), Iutropin (LH), thyrotropin. (TSH) and chorionic gonadotropin (CG). Subsequent papers will address the structure-function behaviour of other members of this increasingly significant family of proteins, including various members of the transforming growth factor-beta (TGF-beta) family of proteins, the activins, inhibins, bone morphogenic growth factor, platelet derived growth factor-beta, nerve growth factor and more than 35 other proteins with similar topological features. In the present review article, specific emphasis has been placed on advances with the glycoprotein hormones (GPHs) that have facilitated greater insight into their physiological functions, molecular structures and most importantly the basis of the molecular recognition events that lead to the formation of hetero-dimeric structures as well as their specific and selective recognition by their corresponding receptors and antibodies. Thus, this review article focuses on the structural motifs involved in receptor recognition and the current techniques available to identify these regions, including the role of immunological methodology, peptide fragment design and synthesis and mutagenesis to delineate their structure-function relationships and molecular recognition behaviour.

Identification of genes expressed in the epithelium of porcine oviduct containing early embryos at various stages of development

As a first step toward elucidation of the action of factors secreted by the epithelium of oviduct, differential display reverse transcription-polymerase chain reaction (DDRT-PCR) was used in this study to identify transcripts of such oviductal factors in gilts carrying various stages of early embryo development post hormone-induced ovulation. A total of 13 differentially expressed transcripts were identified between 50 and 120 hr post-hCG injection (between 1- and 8-cell embryonic stages). Twelve of these transcripts were found to be initially expressed at 96 hr post-hCG injection (at 4-cell embryonic stage) and beyond. Three of such genes were shown by sequence analysis to be the porcine transforming growth factor-alpha, the porcine transforming growth factor-beta-binding protein II and a porcine astral natriuretic factor receptor-like transcript. Only one differentially expressed gene was detected between 50-60 and 85 hr post-hCG injection, and this gene turned out to be the porcine follicle-stimulating hormone receptor. The remaining eight transcripts detected by DDRT-PCR were novel. Moreover, most of these newly expressed genes were found to be turned on at a time coincidental with that of the 4-cell block of porcine embryos cultured in vitro. Our results demonstrate that DDRT-PCR is a feasible approach for rapid identification of genes that are differentially expressed in oviductal epithelium. Some of the genes thus identified may be important for unhindered development of embryos in the oviduct.

Carbohydrate analysis of glycoprotein hormones

Complete carbohydrate composition analysis of glycoprotein hormones, their subunits, and oligosaccharides isolated from individual glycosylation sites can be accomplished using high-pH anion-exchange chromatography combined with pulsed amperometric detection. Neutral and amino sugars are analyzed from the same hydrolyzate by isocratic chromatography on a Dionex CarboPAC PA1 column in 16 mM NaOH. Sialic acid is quantified following mild hydrolysis conditions on the same column in 150 mM sodium acetate in 150 mM NaOH. Ion chromatography on a Dionex AS4A column in 1.8 mM Na(2)CO(3)/1.7 mM NaHCO(3); postcolumn, in-line anion micromembrane suppression; and conductivity detection can be used to quantify sulfate, a common component of pituitary glycoprotein hormone oligosaccharides. Mass spectrometric analysis before and after elimination of oligosaccharides from a single glycosylation site can provide an estimate of the average oligosaccharide mass, which facilitates interpretation of oligosaccharide composition data. Following release by peptide N-glycanase (PNGase) digestion and purification by ultrafiltration, oligosaccharides can be characterized by a high-resolution oligosaccharide mapping technique using the same equipment employed for composition analysis. Oligosaccharide mapping can be applied to the entire hormone, individual subunits, or individual glycosylation sites by varying PNGase digestion conditions or substrates. Oligosaccharide release by PNGase is readily monitored by SDS-PAGE. Site-specific deglycosylation can be confirmed by amino acid sequence analysis. For routine isolation of oligosaccharides, addition of 2-aminobenzamide at the reducing terminus facilitates detection; however, the oligosaccharide retention times are altered. Composition analysis is also affected as the 2-aminobenzamide-modified GlcNAc peak overlaps the fucose peak.

Definition and measurement of follicle stimulating hormone

FSH has a key role in the development and function of the reproductive system and is widely used both diagnostically and therapeutically in developmental and reproductive medicine. The accurate measurement of FSH levels, in patients for diagnosis and monitoring and in therapeutic preparations for clinical use, is essential for safe and successful treatment. Historically, FSH was defined on the basis of classical in vivo endocrine activity, and early therapeutic preparations were calibrated using in vivo bioassays. There was early recognition that reference preparations were required for calibration if the results from different laboratories were to be comparable. In response to the perceived need, the World Health Organization established the first standard for such preparations in 1959. Subsequent developments in biotechnology have led to recognition that there is no single molecule that can be uniquely defined as FSH, and that FSH can induce a range of biological activities. Several highly purified standards for FSH are now available, but discontinuity and heterogeneity of estimates of FSH activity in terms of these standards made using in vitro assays and binding assays have been noted. It is thus essential that any measurement of FSH include specification both of the standard with which the measured FSH is compared and the assay method used for that comparison.

Receptor binding activity and in vitro biological activity of the human FSH charge isoforms as disclosed by heterologous and homologous assay systems: implications for the structure-function relationship of the FSH variants

Follicle-stimulating hormone (FSH) is produced and secreted in multiple molecular forms. These isoforms differ in their oligosaccharide structures, which determine the particular behavior of a given variant in in vitro and in vivo systems. Employing heterologous cell assay systems, this and other laboratories have shown that highly sialylated human FSH variants exhibit lower receptor binding/immunoactivity as well as in vitro bioactivity/immunoactivity relationships than their less sialylated counterparts. It is not known, however, whether this characteristic behavior of the FSH isoforms is reproduced by homologous assay systems, in which unique variants of the receptor are presumptively expressed. To gain further insights into the structure-activity relationship of the various FSH isoforms, we analyzed the capacity of nine charge isoforms obtained after high-resolution chromatofocusing (pH window, 7.10 to <3.80) of anterior pituitary glycoprotein extracts to bind and activate their cognate receptor expressed by naturally occurring heterologous cell systems (rat granulosa cells and seminiferous tubule homogenates) as well as by human embryonic kidney-derived 293 (HEK-293) cells transfected with the human FSH (FSH-R) receptor cDNA. In both (heterologous and homologous) receptor assay systems, the isoforms displaced 125I-labeled FSH from the receptor in a dose-response manner; however, whereas in the heterologous systems, the receptor binding activity varied according to the elution pH value/sialic content of the isoforms, with the less acidic variants exhibiting higher receptor binding activity (r = 0.851 and 0.495 [p < 0.01 and p < 0.05] for the granulosa cell and testicular homogenate receptor assay systems, respectively) than the more acidic/sialylated analogs, in the homologous assay, this relationship was practically absent (r = 0.372, p N.S.). The capacity of the isoforms to induce androgen aromatization by rat granulosa cells followed the same trend shown by its corresponding receptor assay system (r = 0.864, p < 0.01). Interestingly and in contrast to the results observed in the homologous receptor binding assay, the ability of the isoforms to induce cAMP production by HEK-293 cells varied according to their elution pH value, with the more sialylated isoforms exhibiting lower potency than their less acidic counterparts (r = 0.852, p < 0.01). The results yielded by the heterologous assays suggest that the different potency of the isoforms to elicit a biological effect in a naturally occurring receptor system depends primarily on the particular affinity of the receptor molecule for each isoform. The existence of a clear dissociation between receptor binding and signal transduction in the homologous system indicate that this later function is rather related to the different ability of the FSH glycosylation variants to induce and/or stabilize distinct receptor conformations that may permit preferential or different degrees of activation/inhibition of a given signal transduction pathway. Thus, the human FSH receptor-transducer system apparently possesses sufficient versatility to respond in a different manner to glycosylation-dependent diverse FSH signals.

Inhibitory effect of plasma obtained from hypophysectomized and control women on the assay of bioactive luteinizing hormone

The purpose of this study was to determine the effect of components of female plasma on the value of bioactive luteinizing hormone (LH), especially in the presence of low immunological LH value. Using both an immunoradiometric assay (IRMA) and rat Leydig cell bioassay, immunoreactive (I) and bioactive (B) LH were assessed in plasma collected from women during a gonadotrophin releasing hormone (GnRH) test performed on day 7 of a spontaneous cycle. Two modes of response to an acute administration of GnRH were defined: normal production of gonadotrophins (group I) and excessive secretion (group II) associated with a significant difference in the B/I-LH ratio between the two groups. The B/I-LH ratio did not vary with sampling time during the test in either group. The addition of LH-free plasma collected from hypophysectomized women caused a 30% decrease in testosterone production compared to control values (in the presence or absence of hLH standard). A partial restoration of testosterone production was observed if plasma was first treated with PEG 12%. The inhibitory factor(s) was also present in plasma from ovulatory women, even after treatment by an antibody against the entire LH molecule. The effect of normal (A) or low I-LH plasma (B) on testosterone production varied strongly according to the plasma volume added to the bioassay, as well as to plasma treatments. Diethylether treatment caused a 50% decrease in testosterone secretion for plasma B (but not for A) whereas a diminution of the steroidogenesis is observed after a PEG treatment of plasma A (but not for B), suggesting that different inhibitory factors are present in plasmas A and B. Therefore the LH bioactivity measured in the rat Leydig cell assay, in terms of testosterone output, seems to represent a balance between the LH molecule and the presence of inhibitory factors in the plasma.

Regulation of the human menstrual cycle

Our understanding of the regulation of the menstrual cycle has recently improved with the development of various tools of investigation. The cycle is now thought to be determined mainly by the ovary itself, which sends various signals to the pituitary and the hypothalamus. The aim of the cycle is to produce a single mature oocyte each month from puberty to menopause. However, the most common evolution of a follicle is atresia, a consequence of the genetically controlled, ovarian apotosis (or "programmed cell death"). Follicular growth and maturation are mostly independent of gonadotropins, from the stage of primordial follicles to antral follicles. A complete intraovarian paracrine system is implied in this gonadotropin-independent follicular growth, and in the modulation of the actions of the gonadotropins in the ovary. FSH allows the rescue of a minority of follicles from atresia and is indispensable to only the final maturation of the preovulatory follicle. The cyclical variations of the gonadotropins are under the control of ovarian steroids (estradiol and progesterone) and peptides (inhibin). The cycle length is determined by follicular growth and by the fixed life span of the corpus luteum. The mechanism of action of gonadotropins is much better understood since the gonadotropins and their receptor cDNA have been cloned. The recent description of naturally occurring mutations has lead to a better understanding of the role of each gonadotropin, demonstrating the crucial role of FSH in the terminal maturation of the follicles. The ovarian cycle can also be monitored at the level of target tissues of steroids such as the endometrium. The cellular mechanisms of endometrial maturation, under the control of estradiol and progesterone, are better understood. The endometrial maturation is synchronized to follicular development and allows implantation of the conceptus. The genes implied in the implantation of the embryo are being identified (e.g., integrins). Last but not least, the mechanisms of endometrial shedding are being elucidated, especially the role of metalloproteases and angiogenic factors. These concepts will allow the development of new treatments for infertility, the design of new contraceptive techniques, and a better tolerance of treatments using sex steroids, particularly progestin-only pill.