Superfamily of G-protein coupled receptors (GPCRs)--extraordinary and outstanding success of evolution.

The G protein-coupled receptors (GPCRs) are considered as very diverse and also surprisingly successful structures during the whole evolutionary process, being capable of transducing the different forms of "information" within the cell and also between cells, such as different peptides, lipids, proteins, nucleotides, nucleosides, organic odorants and photons. Complex studies as well as two-dimensional crystallization of rhodopsin, their paradigm, led to the creation of a useful model having a common central core, consisting of seven transmembrane helical domains, which undergoes appropriate structural modification during activation and signal transduction. After the complete delineation of the human genome, which is the apogee of human scientific civilization and culture, it was possible to identify more than 800 human GPCR sequences and in parallel analyze 342 unique functional nonolfactory human GPCR sequences with phylogenetic analyses. These results support, with high bootstrap values, the existence of five main families, named by the authors glutamate, rhodopsin, adhesion, frizzle/taste2, and secretin, forming the GRAFS classification system. Positions of the GPCRs in chromosomal paralogous regions indicate the importance of tetraploidizations or local gene duplication events during their creation. Some families of GPCRs show, however, very little or no similarity in the sequence of amino acid chains. They utilize an enormous number of different domains to bind ligands and to activate the appropriate G-proteins. The delicate tuning of their coupling to G proteins is further regulated by splicing, RNA editing and phosphorylation. A number of GPCRs may also form homodimers or heterodimers with structurally different GPCRs and also with membrane-bound proteins having one transmembrane domain. It should also be stressed that not all GPCRs are strictly faithful to G proteins because growing evidence indicates that they can interact directly, via their C-terminal domain, with proteins containing PDZ domains, which are present in the PDZ proteins. These proteins organize the NMDA receptors and some K+ channels while their PDZ domains generally bind 3-4 amino-acid stretches of C-terminal sequences of target proteins. The -S/TXV motif was found in some PDZ target proteins. GPCRs can also interact with the Enabled/VASP homology (EVH)-like domain which interacts directly with group 1 mGluR receptors. Every year brings new very important data in research of these proteins, which should be called "the most successful structures evolved during the whole of animal evolution".

In vivo oestrogenic modulation of Egr1 and Pitx1 gene expression in female rat pituitary gland.

EGR1 and PITX1 are transcription factors required for gonadotroph cell Lhb promoter activation. To determine changes in Egr1 and Pitx1 mRNA levels in central and peripheral pituitary stimulations, an in vivo model based on i.c.v. pulsatile (1 pulse/0.5 h over 2 h) GnRH agonist (1.5 nM buserelin) or antagonist (2 nM antide) microinjections was used. The microinjections were given to ovariectomised and 17ß-oestradiol (E2) (3×20 µg), ERA (ESR1) agonist propyl pyrazole triol (PPT) (3×0.5 mg), ERB (ESR2) agonist diarylpropionitrile (DPN) (3×0.5 mg) s.c. pre-treated rats 30 min after last pulse anterior pituitaries were excised. Relative mRNA expression was determined by quantitative RT-PCR (qRT-PCR). Results revealed a gene-specific response for GnRH and/or oestrogenic stimulations in vivo. Buserelin pulses enhanced Egr1 expression by 66% in ovariectomised rats, whereas the oestradiol-supplemented+i.c.v. NaCl-microinjected group showed a 50% increase in Egr1 mRNA expression. The oestrogenic signal was transmitted via ERA (ESR1) and ERB (ESR2) activation as administration of PPT and DPN resulted in 97 and 62%, respectively, elevation in Egr1 mRNA expression. A synergistic action of GnRH agonist and 17ß-oestradiol (E2) stimulation of the Egr1 gene transcription in vivo were found. GnRHR activity did not affect Pitx1 mRNA expression; regardless of NaCl, buserelin or antide i.c.v. pulses, s.c. oestrogenic supplementation (with E2, PPT or DPN) consistently decreased (by -46, -48 and -41% respectively) the Pitx1 mRNA in the anterior pituitary gland. Orchestrated Egr1 and Pitx1 activities depending on specific central and peripheral regulatory inputs could be responsible for physiologically variable Lhb gene promoter activation in vivo.

[Cu-GnRH--new gonadoliberin (GnRH) analog]. / Cu-GnRH--nowy analogon gonadoliberiny (GnRH).

Our research was concentrated about physiological and structural aspects of metal complexes with GnRH, which were synthetized by Professor Henryk Kozlowski from the Uniwersity of Wroclaw. We found that copper, nickel, zinc and cobalt complexes with GnRH stimulated the release of LH and FSH both in vivo and in vitro. The most stable and active was Cu-GnRH. It also exhibited the higher affinity to specific receptor than GnRH, had higher releasing power for LH and FSH and stimulated differently the intracellular signaling. We suggest, that this complex in highly promissive as a new analog of GnRH with possible application to further research.

Valproate inhibits GnRH-induced gonadotropin release from anterior pituitary cells of male rat in vitro.

OBJECTIVE: Valproate (VPA) a potent antiepileptic drug has been claimed to induce reproductive disturbances in men. Long-term VPA treatment can affect sperm morphology and induce testicular atrophy in non-epileptic rats. It has been reported that VPA reduced testosterone secretion stimulated by hCG in isolated rat Leydig cells. These results suggest direct effect of VPA on testes in rats. However centrally mediated effects at hypothalamo-pituitary level can therefore not be excluded. This study focused on the dose and time-dependent effects of VPA on basal and GnRH-induced LH and FSH release from the primary anterior pituitary cells culture of male rats. MATERIAL AND METHODS: The dose-dependent effect of 10 nM-100 mM of VPA on basal LH release from anterior pituitary cells after 3h of incubation was examined. To determine the time-dependent effects on LH, FSH, TSH and PRL release short (3 h) and long-term (24 h) incubations in the presence of 10 nM, 100 nM and 1 µM of VPA were maintained.To assess whether VPA can affect GnRH-induced LH and FSH release, cells were incubated for 3 h with 10 nM, 100 nM and 1 µM of VPA in the presence of GnRH. The concentration of rLH, rFSH, rPRL and rTSH in incubation medium was determined by RIA method. RESULTS: VPA did not affect the basal LH, FSH, PRL and TSH release from the primary anterior pituitary cells culture of male rats. VPA in concentration 1µM significantly suppressed GnRH-induced LH secretion. However VPA at all tested doses diminished GnRH-induced FSH release. CONCLUSIONS: VPA may diminish gonadotropin release in vitro but this effect can only be achieved after GnRH-dependent specific receptor activation. Both gonadotropins differ in their pattern of response for increasing doses of VPA.

Effect of the polymorphism in 5' UTR region of pig prolactin gene on prolactin gene expression and reproduction performance in the female pig.

OBJECTIVES: The recent genetics and molecular biology progress seems to be a fascinating challenge for the interdisciplinary studies on the effects of genetic changes in gene structure that causes the modification of physiological functions of many important proteins including hormones. Pig prolactin is one of the interesting hormones for this study. AIM OF THE STUDY: The aim of the study was to analyze the mutation in 5'UTR region of the pig prolactin (PRL) gene and to evaluate the effect of this polymorphism on changes in plasma prolactin concentration. RESULTS: It was found that only two individual groups of animals differed by the genotype in examined PRL gene locus - homozygote C/C and heterozygote C/T. PRL plasma concentration was 38.4 ng/ml (for C/T animals) or 42.7 ng/ml (for C/C animals). Animals with C/C genotyped exhibited a tendency to elevate PRL concentration as compared to the C/T group (p< 0.07). CONCLUSIONS: This research combines the genetic, molecular and, in vivo, physiological study which allows focus on the possible relationship between the gene polymorphism and physiological status of animal.

Impaired growth hormone-releasing hormone neurons ultrastructure and peptide accumulation in the arcuate nucleus of mosaic mice with altered copper metabolism.

A progressive decrease in body weight and retarded linear growth observed in mosaic male mice with the mutation linked to X-chromosome (Atp7a(mo-ms)) raised the question whether hypophysiotropic growth axis activity may be affected in these animals. A pathologically developed median eminence ultrastructure with very low somatostatin accumulation as well as an intensive phagocytosis of growth hormone cells observed in the anterior pituitary gland raised the question whether hypothalamic growth hormone-releasing hormone (GHRH) neuronal network is also affected in mosaic mice. In this study an arcuate nucleus GHRH neurons ultrastructure as well as GHRH peptide accumulation in normal and mutant mice were compared. An electron microscopic immunocytochemical method with colloidal-gold labeling was applied to compare the ultrastructural morphology of GHRH neuron and intracellular GHRH peptide distribution. Mosaic mice exhibited a pathologically developed ultrastructure of arcuate nucleus GHRH neurons, defective intracellular peptide localization as well as reduced peptide storage. Obtained results support the crucial role of unaltered copper metabolism in physiological development of hypophysiotropic growth axis activity. Consequently, a pathologically developed GHRH hypothalamic network may impact progressive decrease in body weight and retarded length growth observed in mosaic male mice.

Differential binding of mammalian and salmon GnRHs with rat and carp pituitary receptors.

OBJECTIVES: Receptor binding of GnRH is connected with the stimulation of pituitary gonadotropic cells leading to both the release and biosynthesis of gonadotropins. The binding is connected with the conformational changes in the receptor which induce the specific intracellular signalisation. The study of fish GnRHs and their receptors may give us new knowledge of the complex interplay of different mechanisms involved in neuroendocrine regulation of reproduction. METHODS: Receptor binding of both mGnRH and sGnRH were compared by the study utilizing the displacement method with mGnRH or sGnRH as radioactive tracers. Incubation was performed at 2 degrees C to avoid ligand degradation. RESULTS: The comparative binding of mGnRH and sGnRH with GnRH receptors from the female rat pituitary and female carp pituitary was studied. At the 50% of displacement, the binding of sGnRH to the rat pituitary receptor was very small and in comparison to the binding of mGnRH (100%) was in the range 2-15%. However, the binding of mGnRH to carp pituitary receptors is small in comparison with the binding of sGnRH (100%) and was in the range 5-20%. CONCLUSION: The results demonstrated the differences in binding of different GnRHs to the receptor in rats and carp. This suggests that the structures of GnRH and its receptor undergo co-evolution in different classes of animals.

Polymorphism in genes of growth hormone receptor (GHR) and insulin-like growth factor-1 (IGF1) and its association with both the IGF1 expression in liver and its level in blood in Polish Holstein-Friesian cattle.

BACKGROUND: Polymorphisms in the bovine ghr and igf1 genes. Ghr and igf1 genes have been associated with milk and meat production of cattle. However, the molecular and physiological mechanisms underlying such associations are unknown. The objective of this study was to examine the effects of polymorphisms in 5'-regions of the bovine ghr and igf1 genes on the igf1 gene expression in the liver and on the level of IGF1 in blood of Polish Holstein-Friesian cattle. METHODS: Individual and combined effects of single nucleotide polymorphisms (SNPs) in the 5'noncoding regions of the bovine igf1 and ghr genes on the IGF1 level in blood and igf1 gene expression in liver were examined. One SNP in the igf1 gene and four SNPs in the ghr gene were analyzed. IGF1 level in blood was measured by radioimmunoassay (RIA) in 211 heifers and bulls of Polish Holstein-Friesian cattle (of Black-and-White type). The igf1 gene expression was measured in livers of bulls carrying different igf1 and ghr genotypes (from three to nine animals per genotype) using real-time reverse transcription-PCR methods with the gapdh gene as a reference. RESULTS: We showed that C/T transition in the promoter region of the igf1 gene influences the gene expression; relative igf1 expression was higher for animals with the CC genotype than for those with the TT and CT genotypes. TESS analysis showed that C/T transition in the igf1 gene co-localizes with the NF1 transcription factor binding site. Also, the ghr genotype appeared to significantly influence the igf1 gene expression in the liver, and we found the highest expression for the genotypes: RFLP-AluI (AT), RFLP-Fnu4HI(CC), and RFLP-NsiI(GA), and for the combined ghr genotype: AluI(AT)/ Fnu4HI(CC)/NsiI(GA). We discovered a significant association between the igf1 genotype and the IGF1 blood level. The highest IGF1 content in blood serum was found in CC genotype animals (1024 ng/ml) vs 698 ng/m and 859 ng/min in the TT and CT igf1 genotypes, respectively. Moreover, we noticed significant differences between ghr genotypes. The highest blood levels of IGF1 were for the animals carrying the ghr genotypes: RFLP-AluI(AA), RFLP-Fnu4HI(CC), and RFLP-NsiI(AG). Ghr haplotypes also significantly affected the IGF1 blood level. Animals of the combined ghr genotypes AluI(AA)/AccI(CC)/Fnu4HI(CC)/NsiI(AG) and AluI(AA)/AccI(CT)/Fnu4HI (CC)/ NsiI(AG) had a higher IGF1 concentration in blood than other genotype carriers. CONCLUSIONS: The present results indicate that the effects of polymorphism in the igf1 and ghr genes on cattle milk or meat production traits could be at least partially mediated through their effects on the igf1 gene expression in the liver and the IGF1 level in blood.

Development of real-time PCR assays in the study of gonadotropin subunits, follistatin and prolactin genes expression in the porcine anterior pituitary during the preovulatory period.

OBJECTIVES: Neural control of the anterior pituitary function consists of the interplay of neuropeptides action, gonadal steroid hormones and many other factors. The physiological effect of this regulatory action is the release and synthesis of protein hormones in the precise time and quantity. The main factor responsible for the gonadotropins release and synthesis is the gonadotropin-releasing hormone (GnRH). We must still study the modulation of the synthesis of the gonadotropins subunits - LHbeta, FSHbeta and alpha subunit by different forms of GnRH and by its analogs, in order to better understand the regulation of gonadotropin release and synthesis. THE AIM of this study was to develop real-time PCR assays of five candidate reference genes for normalization purposes in order to quantify target transcripts in anterior pituitary cells during the preovulatory period. Moreover, we focused on the influence of GnRH receptor antagonist (antide) treatment on mRNA expression levels of GPalpha, LHbeta, FSHbeta, FST(follistatin) and PRL(prolactin) genes in these cells. MATERIAL AND METHODS: Anterior pituitary cells were obtained from pituitary glands of four mature pigs at the preovulatory phase. Cells were incubated with or without antide and relative mRNA level of target genes was measured using the Applied Biosystems 7500 Real Time System. For an exact comparison of mRNA quantity, the stability of five reference genes, ACTB, B2M, GAPDH, RPL1, and TOP2B was evaluated to choose the most appropriate reference gene for qRT-PCR normalization in the pituitary cells. Expression stability of reference genes was calculated using the geNorm application. The developed method of PCR assay was applied to study gene expression in pig pituitary cells in short culture. RESULTS: The most stably expressed genes in the pituitary cells were GAPDH and TOP2B. The expression of ACTB, B2M and RPL1 appeared to be highly unstable. After normalization to the GAPDH/TOP2B, results showed that the mRNA expression of the FSHbeta gene was highest in comparison with LHbeta, GPalpha, FST and PRL genes (p<0.005). Pre-treatment of cells by the antide resulted in lower mRNA expression of these genes, while FSHbeta mRNA had a significantly lower expression (p<0.05) in comparison with control. CONCLUSIONS: Real-time PCR analysis of the expression of LHbeta, FSHbeta, alpha subunit, follistatin and prolactin genes in porcine anterior pituitary cells during the preovulatory period is suitable for the study of modulatory action of metal complexes with GnRH on the expression of these genes.

Involvement of copper in female reproduction.

Copper (Cu) is one of the essential trace metals which are necessary in maintaining the functioning of living organisms. The current knowledge on the role of copper in animal reproduction is presented in the article. Our studies have shown that complexes of copper (Cu²+) with gonadotropin-releasing hormone (GnRH) are even more effective in the release of LH than native GnRH. Moreover, Cu-GnRH is more potent in inducing in vivo release of FSH than LH. Copper complexes with GnRH interact with GnRH receptors (GnRHR) and modulate intracellular signaling in the gonadotrope cells of the anterior pituitary. Copper plays also a significant role in maintaining normal fetus development in mammals.

Single base substitution in growth hormone receptor gene influences the receptor density in bovine liver.

OBJECTIVES: Nucleotide sequence polymorphisms in the coding gene regions may influence the biological properties of proteins encoded by a gene. The A/T substitution in exon 8 of the growth hormone receptor (GHR) gene results in changed amino acid sequence 279 (Phe/Tyr) in the transmembrane domain of the receptor protein and therefore could influence its functional parameters. We searched for the relationship between the A/T nucleotide polymorphism in the GHR gene the receptor binding capacity and dissociation constant. METHODS: Nucleotide sequence variations in the exon 8 (coding for the transmembrane domain of the receptor) of the bovine GHR gene and in fragments of adjacent introns were analysed using PCR-SSCP and sequencing techniques. GH receptor binding capacity (Bmax) and dissociation constant (Kd) for GHR were determined by the Scatchard analysis in livers of ten bulls carrying the AA or AT GHR genotypes. RESULTS: Two single nucleotide polymorphisms (SNPs) were identified--the C/T transition in intron 8 at position 863+32 and the A/T transversion in exon 8 at position 836, the latter resulting in Phe/Tyr amino acid substitution in the receptor protein. The results showed significant differences in the GHR binding capacity between these genotypes. Bmax was significantly greater (p< or =0.01) in bulls carrying TT genotype of GHR in comparison to those with the AT genotype. No significant differences in the dissociation constants (Kd) were found. CONCLUSION: Our results demonstrated that single base substitution in the transmembrane domain encoding region of GH receptor gene may influence the physiological properties of the receptor.

LH release by Cu and Ni salts and metal-GnRH complexes, in vitro.

The present studies were undertaken to examine the effect of copper and nickel salts and their complexes with GnRH on LH release from the pig anterior pituitary cells in vitro. The potency of Cu-GnRH and Ni-GnRH binding to GnRH receptors with iodinated GnRH as a radioactive tracer was also verified. The incubation of pig pituitary cells with Cu and Ni acetate salts showed no effect of the studied ions on LH release at any concentration used. However, nickel salt at a lower dose (10(-10) and 10(-9) M) tended to decrease LH output. By contrast, the native GnRH as well as its metal complexes significantly stimulated LH release after three hours of treatment and Cu-GnRH was found to be the most effective. The results showed that Cu and Ni complexes with GnRH but not their acetate salts are effective in LH release from pig pituitary cells collected from adult female pigs.

Growth hormone cell phagocytosis in adenohypophysis of mosaic mice: morphological and immunocytochemical electron microscopy study.

An electron microscopy immunocytochemical study was performed to determine the expression pattern of growth hormone (GH) in mosaic mutant mice adenohypophysis. In normal condition GH was restricted to the secretory granules of all growth hormone cells. Mosaic mice adenohypophysis contained growth hormone cells which have distinctive GH labeled secretory granules at the level seen in control animals. Ultrastructurally, some GH cells of mosaic mice presented abnormalities, but labeling intensity of secretory granules in these cells was always comparable to the basal condition. The striking findings presence of two forms (simple and activated) of folliculo-stellate cells (FS) in close association trough gap or tight junction with GH cells localized especially near the perivascular space. Frequently, in cytoplasm of FS cells, large clusters containing fragments of GH labeled cell were present. Additionally, the existence of large intracellular, electron-lucent spaces, with remnant cellular material in parenchyma of mosaic mutant mice adenohypophysis could suggest intensive process of GH-cell destruction. Our electron microscopy immunocytochemical results provide evidence for loss of GH cells in mosaic mice by phagocytosis. We suppose that impaired body growth observed in mosaic mutant male rats may be, at least partially, a consequence of an alteration in somatotropic axis activity. Loss of GH cells in mosaic mice by phagocytosis supported by FS cells may contribute to this effect.

Vasoactive intestinal peptide modulates luteinizing hormone subunit gene expression in the anterior pituitary in female rat.

The direct monosynaptic pathway which exists between vasoactive intestinal peptide (VIP) and GnRH neurons in the hypothalamic preoptic area provides a neuroanatomical background for the modulatory effects of VIP exerted on GnRH neurons activity. Though central microinjection of VIP revealed its involvement in the modulation of LH release pattern, there is a lack of data concerning a possible VIP influence on the alpha and LHbeta subunit gene expression in the pituitary gland. Using a model based on intracerebroventricular pulsatile peptide(s) microinjections (1 pulse/h [10 microl/5 min] over 5 h) the effect of exogenous VIP (5 nM dose) microinjection on subunits mRNA content in ovariectomized/oestrogen-pretreated rats was studied. Subsequently, to obtain data concerning the involvement of GnRH and VIP receptor(s) in the regulation of alpha and LHbeta subunit mRNA expression, OVX/estrogen-primed rats received a pulsatile microinjections of 5 nM VIP with 3 nM antide (GnRH receptor antagonist) or 5 nM VIP with 15 nM VIP 6-28 (VIP receptor antagonist). In this case, substances were given separately with a 30 min lag according to which each antagonist pulse preceded a VIP pulse. Northern-blot analysis revealed that VIP microinjection resulted in a decreased alpha and LHbeta mRNA content in pituitary gland and this effect was dependent on GnRH receptor activity. Moreover, obtained results indicated that centrally administered VIP might operate through its own receptor(s) because a receptor antagonist, VIP 6-28, blocked the inhibitory effect of VIP exerted on both LH subunit mRNA content and LH release.

Different signaling in pig anterior pituitary cells by GnRH and its complexes with copper and nickel.

Gonadotropin releasing hormone (GnRH) is an essential factor in the regulation of synthesis and release of pituitary gonadotropins. After binding to specific receptors and coupling with G proteins, it triggers the intracellular signaling involving the synthesis of inositol phosphates and diacylglycerol. Previously we have showed that certain metal complexes with GnRH, i.e. copper (Cu-GnRH) and nickel (Ni-GnRH) are able to bind to the GnRH receptors. The intracellular signalling of these complexes, however, has not been yet elucidated. In this experiment, the ability of the Cu-GnRH and Ni-GnRH complexes to modulate cAMP synthesis and phosphoinositols formation in the pig anterior pituitary cells in vitro was studied. The native GnRH and its metal complexes stimulated the luteinizing hormone (LH) release, but only the effect of Cu-GnRH was found to be a dose-dependent. The metal complexes did not significantly influence inositol phosphates accumulation, while their effect on cAMP synthesis was significantly more potent than that of GnRH alone. We conclude that the Cu-GnRH and Ni-GnRH complexes increase LH release in the porcine pituitary cells although their intracellular signaling is different from that of the native GnRH. It seems that metal complexes with GnRH deserve more attention in further studies.

Long form leptin receptor mRNA expression in the hypothalamus and pituitary during early pregnancy in the pig.

OBJECTIVE: The aim of this study was the detection and location of long form leptin receptor (OB-Rb) in different area of hypothalamus and pituitary in the pig during early pregnancy. SETTINGS AND DESIGN: Expression of OB-Rb was examined by RT-PCR in the different area of hypothalamus: medial basal hypothalamus (MBH), preoptic area (POA), stalk median eminence (SME), as well as pituitary: the anterior (AP) and posterior (NP) lobe collected from gilts at days 14-16 (n=4) and 30-32 (n=4) of pregnancy. RESULTS: The results showed that OB-Rb mRNA was expressed in the hypothalamus (MBH, POA and SME), pituitary (AP, NP) and adipose tissue in the pig during early pregnancy (at days 14-16 and 30-32). CONCLUSION: These findings support the idea that leptin might play a role in the regulation of the hypothalamic-pituitary axis activity, and consequently in the control of pregnancy during critical period of embryo implantation in the pig.

Further structural analysis of GnRH complexes with metal ions.

MALDI-TOF mass spectrometry, 1H NMR spectrometry, the continuous variation method and molecular modeling by MM3 calculation confirmed our earlier studies showing that gonadotropin-releasing hormone (GnRH) forms complex with copper(II) ion with the binding ratio 1:1. The copper(II) complex formed at physiological pH has a square planar configuration and GnRH complexes with nickel(II) and cobalt(II) ions are less stable than that of copper(II).

Cobalt complex with GnRH stimulates the LH release and PKA signaling pathway in pig anterior pituitary cells in vitro.

Metal complexes with GnRH were shown to interact with GnRH receptors in pituitary cells. In the present study we examined the effects of GnRH and its cobalt complex form (Co-GnRH) on LH secretion and generation of second messengers, namely inositol phosphates (IPs) and cAMP, in porcine pituitary cells in vitro. The cells were obtained from gilt pituitary at the pre-ovulatory phase of estrous cycle and cultured for 72 h before challenge with GnRH or Co-GnRH. Both substances induced a significant increase in LH release that was detectable after 60 min (P<0.05) of treatment, with the Co-GnRH complex being more efficient than GnRH at 180 min (P<0.01). GnRH and Co-GnRH were equally effective at 10(-8)M (P<0.01), however, at the lowest (10(-9)M) as well as the highest (10(-7)M) concentrations tested, Co-GnRH was more potent than its native counterpart (P<0.01). Interestingly, Co-GnRH revealed twice more efficient than GnRH at stimulating cAMP production, an effect which was detectable in cells after 1h-incubation (P<0.001). In contrast, while native GnRH induced a rapid increase (P<0.05) in IPs no such effect of Co-GnRH was observed. These data demonstrate that Co-GnRH and GnRH differentially effect on the signaling pathway in porcine gonadotropes and suggest that in these cells, the releasing action of Co-GnRH results from the mediation via the cAMP/protein kinase A second messenger system.

Leptin gene expression in the hypothalamus and pituitary of pregnant pigs.

BACKGROUND: Leptin, the 16-kDa peptide hormone product of the ob gene, is a regulatory hormone secreted mainly by adipose tissue. Recent studies have shown leptin production by other tissues, including rat hypothalamus, rat and human pituitary, rat skeletal muscle, kidney and stomach, human and porcine placenta, human mammary epithelial cells as well as endometrial tissues. This hormone is a central modulator of food intake, metabolism and neuroendocrine functions. OBJECTIVES: The aim of the study was to detect and locate porcine leptin gene expression in the different areas of the hypothalamus and pituitary on days 14-16 and 30-32 of pregnancy in pigs. METHOD: Leptin gene expression was analysed by RT-PCR method. PCR products were subjected to sequencing analysis. RESULTS: Leptin mRNA was expressed in the medial basal hypothalamus, preoptic area, stalk median eminence, anterior pituitary, posterior pituitary and adipose tissue on days 14-16 and 30-32 of pregnancy. Sequence analysis of the 258 bp product from the hypothalamus and pituitary confirmed 99% homology with the corresponding region of porcine leptin cDNA sequence. CONCLUSION: Leptin mRNA expression in the porcine hypothalamus and pituitary gland implies its paracrine and/or autocrine role in the regulation of hypothalamic-pituitary axis activity.

Impaired somatostatin accumulation within the median eminence in mice with mosaic mutation.

OBJECTIVES: The mosaic mutation (Atp7a(mo-ms)) linked to X-chromosome is caused by changes in the Atp7a gene encoding CPx-type protein responsible for the ATP-dependent copper transport across cell membranes. Mosaic mutant males represent an animal model for Menkes disease in humans. Starting from the eighth day of life the mosaic males exhibit a progressive decrease in body weight with poor viability and progressive paresis of the hind limbs. In order to examine whether hypothalamic somatostatin metabolism may be different in normal and copper deficient mice, somatostatin accumulation at the level of median eminence in 14 days old normal and mosaic mutant males was compared. METHODS: An electron microscopic immunocytochemical study on ultrathin brain slices was performed according to post-embedding immunogold procedure. RESULTS: In non-mutant animals somatostatin has been detected in many synapses within median eminence. Gold particles moderately decorated synaptic vesicles and mitochondria. In mosaic mutant animals somatostatin expression within the median eminence was very low and only a few gold particles represented somatostatin. Particles were sporadically associated with synaptic vesicles, mitochondria or cytoskeleton elements. Moreover, pre- and post- synaptic parts of synapses were very often swollen. CONCLUSION: Our data demonstrating that copper deficiency leads to the pathological changes within the median eminence ultrastructure and severe impairment of somatostatin expression suggest that this trace metal is an important element necessary for normal neurohormonal brain development.