GH Gene Expression Research Articles

Purification, cDNA cloning, and characterization of ghrelin in channel catfish, Ictalurus punctatus

The ghrelin peptide and cDNA encoding precursor protein were isolated from the stomach of a channel catfish, Ictalurus punctatus. Catfish ghrelin is a 22-amino acid peptide with a sequence of GSSFLSPTQKPQNRGDRKPPRV. The third serine residue has been modified by n-decanoic acid and unsaturated fatty acids; however, an octanoylated form could not be identified. The carboxyl end of the peptide possessed an amide structure. A Gly-extended, non-amidated 23-amino acid ghrelin (ghrelin-Gly) was also isolated. Real-time quantitative PCR analysis revealed high levels of gene expression in the stomach and moderate levels in the pancreas and gall bladder. Intraperitoneal (IP) injection of ghrelin increased plasma GH levels in the catfish, but the effect of ghrelin-Gly was more potent than that of amidated ghrelin. Furthermore, IP injection with both amidated ghrelin and ghrelin-Gly caused a significant increase in pituitary GH mRNA expression over a 3-h period. These results indicate that ghrelin is present in catfish and stimulates GH gene expression and GH release in channel catfish.

Pit-1 Gene Inhibition Using Small Interfering RNAs in Rat Pituitary GH Secreting Cell Line

RNA interference (RNAi) provides a powerful method for gene silencing in eukaryotic cells. We report on an RNAi technique-induced Pit-1 gene silencing in a GH-secreting cell line MtT/S using duplexes of 21-nt RNAs. By immunocytochemical analysis, the decrease in Pit-1 immunoreactivity was observed in a fraction of siRNA transfected MtT/S cells, while actin and tubulin showed no change in expression following transfection. Moreover, the double staining of Pit-1 and GH indicated that GH production was reduced only in MtT/S cells in which Pit-1 immunoreactivity was decreased by transfection. These results suggested that functional specific knock-down of Pit-1 was induced by transfection of siRNA. Together with the defects of somatotropic lineage and hypoplastic phenotypes in Snell dwarf mice and the transfection experiments using Pit-1 antisense oligonucleotides, our experiments support the theory that Pit-1 plays a crucial role in GH gene expression in individual cells.

The Zinc Finger Ikaros Transcription Factor Regulates Pituitary Growth Hormone and Prolactin Gene Expression through Distinct Effects on Chromatin Accessibility

The Ikaros transcription factors perform critical functions in the control of lymphohematopoiesis and immune regulation. Family members contain multiple zinc fingers that mediate DNA binding but have also been implicated as part of a complex chromatin-remodeling network. We show here that Ikaros is expressed in pituitary mammosomatotrophs where it regulates the GH and prolactin (PRL) genes. Ikaros was detected by Northern and Western blotting in GH4 pituitary mammosomatotroph cells. Wild-type Ikaros (Ik1) inhibits GH mRNA and protein expression but stimulates PRL mRNA and protein levels. Ikaros does not bind directly to the proximal GH promoter but abrogates the effect of the histone deacetylation inhibitor trichostatin A on this region. Ikaros selectively deacetylates histone 3 residues on the proximal transfected or endogenous GH promoter and limits access of the Pit1 activator. In contrast, Ikaros acetylates histone 3 on the proximal PRL promoter and facilitates Pit1 binding to this region in the same cells. These data provide evidence for Ikaros-mediated histone acetylation and chromatin remodeling in the selective regulation of pituitary GH and PRL hormone gene expression.

Binding of AP-2 and ETS-domain family members is associated with enhancer activity in the hypersensitive site III region of the human growth hormone/chorionic somatomammotropin locus.

The human GH gene family is specifically expressed in somatotrophs of the anterior pituitary and placental syncytiotrophoblast. Two nuclease-hypersensitive sites, HS III and HS V, are associated with a region of chromatin located 28 and 30 kb upstream of the pituitary GH gene transcription initiation site (+1) in both pituitary and placenta nuclei. A role for this region in pituitary GH gene expression has been reported, but the potential relevance to placental gene expression has not been determined. Deletion analysis of a 5.2-kb region (nucleotides - 27,568/-32,746) containing HS III to V-related sequences localized significant enhancer activity to a 574-bp HS III fragment (nucleotides -27,676/-28,249) in multiple transfected cell lines. Four nuclease-protected regions [footprints (FP) 1-4] were identified in the 574-bp fragment. FP2 and FP3 were detected with placenta cell nuclear protein, whereas FP1 and FP4 were observed with placental and nonplacental cell nuclear extract. Disruption of FP1 had no effect on heterologous promoter activity in transfected pituitary and placental cells, whereas loss of FP2 and FP3 resulted in modest increases in placental cells, reflecting the presence of repressor activity associated with these regions in vitro. In contrast, disruption of the FP4 region by mutation or deletion significantly reduced enhancer activity. As a result, 30-fold enhancer activity was localized to a 41-bp region in transfected placental tumor cells. Binding of candidate proteins, activator protein (AP)-2 (FP3) and Elk-1 (FP4), was confirmed using competition assays with specific oligonucleotides and antibodies. Moreover, these factors were associated with the hyperacetylated HS III region in human pituitary [activator protein 2 (AP-2) and Elk-1] and term placenta (AP-2) chromatin. These data implicate AP-2 and ETS-domain family members in the regulation of the GH/CS locus and raise the possibility that different complexes form in the HS III region in placenta and pituitary cells.

The effects of GH-releasing hormone/somatostatin on the 5'-promoter activity of the GH gene in vitro.

The two hypothalamic hormones, GH-releasing hormone (GHRH) and somatostatin (SRIF), are known to regulate GH secretion. However, the effects of these hormones on GH gene expression are not completely clear, partly because of the lack of appropriate host cells maintaining the original characteristics of the somatotroph. Since MtT/S, a pure somatotroph cell line, has become available, the effects of GHRH and SRIF on GH gene transcription have been studied using a subclone of MtT/S (MtT/SGL), in which the GH gene 5'-promoter-luciferase fusion gene was stably incorporated. The expression of GHRH receptor and SRIF receptor subtypes was also studied by RT-PCR. The results showed that MtT/SGL cells intrinsically expressed the functional GHRH receptor and all of the SRIF receptor subtypes. The expression of GHRH receptor was markedly enhanced by glucocorticoid pretreatment and, in the presence of corticosterone and 3-isobutyl-1-methylxanthine, GHRH (at or above 100 pM) stimulated GH gene 5'-promoter activity in a dose-dependent manner. On the other hand, SRIF (100 nM) significantly antagonized the effect of GHRH, which was completely reversed by pretreatment with pertussis toxin (50 ng/ml). Taken together, the present data indicated that both GHRH and SRIF are involved in the transcriptional regulation of the GH gene, and that the effect of SRIF is mediated through pertussis toxin-sensitive G protein. The MtT/SGL cell line is a good in vitro model for studying the molecular mechanisms of GH gene transcription by GHRH and/or SRIF.

IGF-I regulates pro-opiomelanocortin and GH gene expression in the mouse pituitary gland.

IGF-I is expressed in somatotrophs, and IGF-I receptors are expressed in most somatotrophs and some corticotrophs in the mouse pituitary gland. Our recent study demonstrated that IGF-I stimulates the proliferation of corticotrophs in the mouse pituitary. These results suggested that somatotrophs regulate corticotrophic functions as well as somatotrophic functions by the mediation of IGF-I molecules. The present study aimed to clarify factors regulating pituitary IGF-I expression and also the roles exerted by IGF-I within the mouse anterior pituitary gland. Mouse anterior pituitary cells were isolated and cultured under serum-free conditions. GH (0.5 or 1 microg/ml), ACTH (10(-8) or 10(-7) M), GH-releasing hormone (GHRH; 10(-8) or 10(-7) M), dexamethasone (DEX; 10(-8) or 10(-7) M) and estradiol-17beta (e2; 10(-11) or 10(-9) M) were given for 24 h. IGF-I mRNA levels were measured using competitive RT-PCR, and GH and pro-opiomelanocortin (POMC) mRNA levels were measured using Northern blotting analysis. GH treatment significantly increased IGF-I mRNA levels (1.5- or 2.1-fold). ACTH treatment did not alter GH and IGF-I mRNA levels. IGF-I treatment decreased GH mRNA levels (0.7- or 0.5-fold), but increased POMC mRNA levels (1.8-fold). GH treatment (4 or 8 microg/ml) for 4 days increased POMC mRNA levels. GHRH treatment increased GH mRNA levels (1.3-fold), but not IGF-I mRNA levels. DEX treatment significantly decreased IGF-I mRNA levels (0.8-fold). e2 treatment did not affect IGF-I mRNA levels. GH receptor mRNA, probably with GH-binding protein mRNA, was detected in somatotrophs, and some mammotrophs and gonadotrophs by in situ hybridization using GH receptor cDNA as a probe. These results suggested that IGF-I expression in somatotrophs is regulated by pituitary GH, and that IGF-I suppresses GH expression and stimulates POMC expression at the transcription level. Pituitary IGF-I produced in somatotrophs is probably involved in the regulation of somatotroph and corticotroph functions.

Locally produced growth hormone in canine insulinomas

The production and release of GH has been demonstrated in a variety of extra-pituitary tissues. In this respect insulin-producing pancreatic tumours are also of interest because it has been observed that GH may promote islet cell proliferation. However, these effects have only been related to GH of pituitary origin and the possibility of local production of GH with autocrine-/paracrine effects has not been considered. In this study, a reverse transcriptase polymerase chain reaction (RT-PCR) was used to demonstrate the presence of GH mRNA in pancreatic tissue of five healthy dogs and insulinomas of 14 dogs. After Southern blotting of the RT-PCR products, blots were hybridized using a canine-specific GH-probe and quantified using phosphor imaging. GH gene expression was further demonstrated by in situ hybridization using a canine digoxigenin-labelled GH-specific cDNA probe. In addition, GH immunohistochemistry was performed. In five samples of normal pancreatic tissue a weak hybridization signal was found. This signal was significantly higher in nine of 12 primary tumours. In ten of 11 metastases there was a positive hybridization signal, and this signal was also significantly higher than in the primary tumours. In situ hybridization in one sample demonstrated that GH mRNA was only produced in the tumour cells. The local production of GH was confirmed by positive staining of tumour tissue with anti-GH antibodies in ten of 12 samples. It is concluded that canine insulinomas express the gene encoding GH mRNA. The locally produced GH may have an autocrine/paracrine effect on tumour progression. The relatively high expression levels in metastases of these tumours may be related to the low inhibitory influence of somatostatin outside the pancreas.

High stromal and epithelial human gh gene expression is associated with proliferative disorders of the mammary gland.

We have demonstrated and localized human GH (hGH) gene expression in surgical specimens of normal human mammary gland and in proliferative disorders of the mammary gland of increasing severity using sensitive in situ RT-PCR methodology. hGH mRNA identical to pituitary hGH mRNA was first detected by RT-PCR of RNA derived from samples of normal human mammary gland. Cellular localization of hGH gene expression in the normal mammary gland exhibited restriction to luminal epithelial and myoepithelial cells of the ducts and to scattered stromal fibroblasts. We subsequently examined the expression of the hgh gene in three progressive proliferative disorders of the human mammary gland, i.e. A benign lesion (fibroadenoma), a pre-invasive stage (intraductal carcinoma) and an invasive ductal carcinoma. hGH mRNA was readily detected in the tumoral and non-tumoral epithelial components and also in cells of the reactive stroma including fibroblasts, myofibroblastic and myoepithelial cells, inflammatory infiltrate lymphocytes and endothelial cells in areas of neovascularization. In all three proliferative disorders examined, the intensity of the cellular labeling observed in both the epithelial and stromal compartments was always stronger compared with that in adjacent normal tissue. hGH protein was also present in significantly higher concentration in extracts derived from proliferative disorders of the mammary gland compared with extracts derived from normal mammary gland. We also examined hGH gene expression in axillary lymph nodes not containing and containing metastatic mammary carcinoma. hGH gene expression was evidenced in metastatic mammary carcinoma cells and in reactive stromal cells by both in situ hybridization and in situ RT-PCR. In contrast, in lymph nodes not containing metastatic mammary carcinoma, hGH mRNA was detected only by use of in situ RT-PCR. Thus, increased expression of the hGH gene in the epithelial component and the de novo stromal expression in proliferative disorders of the mammary gland are suggestive of a pivotal role for autocrine hGH in neoplastic progression of the mammary gland.

Regulation of prolactin, GH, and Pit-1 gene expression in anterior pituitary by Pitx2: An approach using Pitx2 mutants.

The transcription factor Pitx2 is required for the morphogenesis of anterior structures such as the eye, teeth, and anterior pituitary. We investigated the functional properties of Pitx2 missense mutants previously reported in Axenfeld-Rieger syndrome, using reporter genes under the control of pituitary target gene [human (h)PRL, hGH, hPit-1] promoters transfected in nonpituitary and pituitary cell lines. The five mutants appeared to be transcriptionally defective despite conserved DNA-binding in CV1 cells. In addition, one mutation, R91P, almost completely blocked the wt-Pitx2-induced activation of the target promoters, prevented the Pitx2/Pit-1 synergistic activation of the hPRL promoter, and was able to counteract the Pitx1-driven transactivation effects. The dominant negative properties of this mutant were further established in cells endogenously expressing Pitx2 because transfection of R91P in GH4C1 somatolactotroph cells resulted in a dose-dependent inhibition of basal activities of the pituitary promoters. These results, which show that Pitx2 mutants are defective in activating pituitary target genes, confirm the critical role of this homeodomain factor in the differentiated functions of the pituitary somatolactotroph cells. Furthermore, these results might form the basis for future experiments because dominant negative forms of Pitx2 such as R91P might provide instructive tools to further delineate the detailed mechanisms mediating Pitx2 functions in cell proliferation and differentiation.

Regulation of Prolactin, GH, and Pit-1 Gene Expression in Anterior Pituitary by Pitx2: An Approach Using Pitx2 Mutants

Regulation of Prolactin, GH, and Pit-1 Gene Expression in Anterior Pituitary by Pitx2: An Approach Using Pitx2 Mutants

Leptin regulates GH gene expression and secretion and nitric oxide production in pig pituitary cells.

The aim of this study was to investigate the direct effect of leptin on GH gene expression and secretion and the role of nitric oxide as a possible mediator in pig anterior pituitary cells. Pituitary cells from adult sows were treated for 4 or 24 h with rhleptin (from 0.1 nM to 1 microM) alone or in association with GHRH (10 nM) or hexarelin (10 nM). At the end of incubation, medium was collected for GH and nitric oxide determination by ELISA and Griess test, respectively. Total RNA was collected from cells, and GH gene expression was measured by RT-PCR. Leptin significantly (P < 0.001) stimulated GH secretion in both incubation periods. The maximum response was induced by 10 nM leptin; furthermore, a significant interaction (P < 0.002) between leptin and GHRH (P < 0.03) and between leptin and hexarelin was observed when the molecules were used in association. GH gene expression was significantly increased (at least P < 0.05) by hexarelin, GHRH, and leptin (1000 and 100 nM) after 24 h of treatment. Leptin (10 nM and 1 microM) significantly (P < 0.05) increased nitric oxide production, whereas S-nitroso-N-acetyl-penicillamine (from 0.01-1000 nM) significantly (P < 0.05) stimulated GH secretion. These data demonstrate that leptin directly influences GH regulation at the pituitary level, and nitric oxide may be involved in this function.

Leptin Regulates GH Gene Expression and Secretion and Nitric Oxide Production in Pig Pituitary Cells

The aim of this study was to investigate the direct effect of leptin on GH gene expression and secretion and the role of nitric oxide as a possible mediator in pig anterior pituitary cells. Pituitary cells from adult sows were treated for 4 or 24 h with rhleptin (from 0.1 nm to 1 μm) alone or in association with GHRH (10 nm) or hexarelin (10 nm). At the end of incubation, medium was collected for GH and nitric oxide determination by ELISA and Griess test, respectively. Total RNA was collected from cells, and GH gene expression was measured by RT-PCR. Leptin significantly (P < 0.001) stimulated GH secretion in both incubation periods. The maximum response was induced by 10 nm leptin; furthermore, a significant interaction (P < 0.002) between leptin and GHRH (P < 0.03) and between leptin and hexarelin was observed when the molecules were used in association. GH gene expression was significantly increased (at least P < 0.05) by hexarelin, GHRH, and leptin (1000 and 100 nm) after 24 h of treatment. Leptin (10 nm and 1 μm) significantly (P < 0.05) increased nitric oxide production, whereas S-nitroso-N-acetyl-penicillamine (from 0.01–1000 nm) significantly (P < 0.05) stimulated GH secretion. These data demonstrate that leptin directly influences GH regulation at the pituitary level, and nitric oxide may be involved in this function.

Effects of Interleukin-1-Beta, Interleukin-6 and Tumor Necrosis Factor-Alpha, Alone or in Association with Hexarelin or Galanin, on Growth Hormone Gene Expression and Growth Hormone Release from Pig Pituitary Cells

Objective: We studied the effects of IL-1β, IL-6 and TNF-α on GH gene expression and secretion with or without galanin and hexarelin. Methods: Pituitary cells from adult pigs were treated with IL-1β, IL-6 or TNF-α (1, 10 and 100 ng/ml), alone or in association with galanin or hexarelin (10^–8M): GH mRNA was measured by RT-PCR and GH secretion by ELISA. Results: IL-1β (1, 10 and 100 ng/ml) and IL-6 (1 and 10 ng/ml) significantly (p < 0.05) enhanced GH output. IL-1β and TNF-α (1 and 10 ng/ml) reduced (p < 0.05) the galanin-induced GH secretion and IL-6 (10 ng/ml) potentiated the effect of both GH releasers (p < 0.05). GH gene expression was increased only by IL-6 at the concentrations of 1 and 10 ng/ml, either alone or in association with both galanin and hexarelin. Conclusions: We hypothesize that cytokines may play a paracrine/autocrine role in GH regulation in the pituitary independently from the intracellular pathways of the GH secretagogues.

Foreign GH gene expression in GH transgenic salmon

Foreign GH gene expression in GH transgenic salmon

GH gene expression in the submaxillary gland in normal and Ames dwarf mice.

High local GH-releasing hormone (GHRH) levels are capable of inducing transdifferentiation in salivary cells to synthesize GH. However, the factors implicated in this process remain unknown. To study this subject, normal and Ames dwarf mice were implanted in the submaxillary gland with a slow release pellet releasing 21 microgram GHRH (1-29)-NH(2)/day for 2 months. Control animals received placebo pellets at the same site. After 60 days, heart blood was collected and submaxillary glands were removed. Circulating levels of GH and IGF-I were significantly decreased (P<0.05) in dwarf mice in comparison with controls, and GHRH treatment did not modify either of these two parameters. Controls carrying GHRH pellets showed a significantly higher GH content (P<0.05) in the submaxillary gland than the placebo-treated normal mice. There were no differences between the IGF-I concentrations of placebo- and GHRH-treated salivary tissue from normal mice. Analysis of GH mRNA by RT-PCR followed by Southern blot revealed that GH transcripts were present in the salivary gland samples carrying the placebo pellets in both normal and dwarf mice. The expression of GH was significantly (P<0.05) increased by the GHRH pellets in salivary tissue from normal mice, but not in submaxillary glands from dwarf mice. Pit-1 mRNA was not detected in the GHRH-treated glands of normal and dwarf mice by RT-PCR or by Southern blot. Using these highly sensitive methods, we have been able to detect the transcription of both GH and Pit-1 in pituitaries from Pit-1-deficient Ames dwarf mice. The present experiment demonstrates that salivary tissue synthesizes GH when it is exposed to the influence of GHRH. Both basal and GHRH-induced salivary GH expression appear to be independent of Pit-1.

Blue gourami β GTH-I, β GTH-II and GH gene expression affected by GNRH analog

Blue gourami β GTH-I, β GTH-II and GH gene expression affected by GNRH analog

Effect of neonatal and adult testosterone treatment on the cellular composition of the adult female rat anterior pituitary.

The adult female pituitary has significantly more lactotrophs than that of the male, while the later has a higher percent of somatotrophs. It is clear that GH and prolactin (PRL) gene expression and somatotroph and lactotroph proliferation are modulated by the postpubertal hormone environment; however, the role of the neonatal steroid environment in this process is not known. We have used in situ hybridization to determine the number of GH and PRL mRNA-containing cells, as well as the level of expression of these two hormones, in response to neonatal and adult testosterone treatment. Female rats exposed to testosterone during the neonatal period, adulthood or both periods, as well as normal females and males were used. Exposure to testosterone during the neonatal period significantly increased the percentage of somatotrophs (ANOVA: P<0. 005) and decreased that of lactotrophs in the adult female rat (ANOVA: P<0.001). Adult testosterone treatment had no significant effect on the percentage of somatotrophs. The percentage of lactotrophs was significantly increased by adult testosterone only in those rats also exposed to neonatal testosterone. PRL mRNA concentrations, as reflected by silver grains/cell, were reduced by neonatal testosterone and increased by adult testosterone treatment (ANOVA: P<0.0001). Overall PRL mRNA levels, measured by densitometry, were also reduced by neonatal testosterone exposure, but adult testosterone had no effect (ANOVA: P<0.001). GH mRNA levels per cell, as reflected by silver grains/cell, were increased by adult testosterone, while neonatal testosterone treatment had no effect. Overall GH mRNA levels per unit area, determined by densitometry measurements, were increased by both neonatal and adult testosterone treatment, with the combination of these two treatments resulting in adult females having levels indistinguishable from intact males (ANOVA: P<0.003). These results suggest that, in combination with postpubertal sex steroids, the neonatal gonadal steroid environment plays an important role in determining anterior pituitary hormone synthesis and cellular composition.

Mouse growth hormone transcription factor Zn-16: unique bipartite structure containing tandemly repeated zinc finger domains not reported in rat Zn-15

Rat Zn-15 is a transcription factor activating GH gene expression by synergistic interactions with Pit-1, named for 15 DNA-binding zinc fingers, including fingers IX, X, and XI that are responsible for GH promoter binding. In this study, a mouse cDNA for Zn-15 was characterized. The predicted 2192-amino acid mouse protein is 89% identical to rat (r) Zn-15 overall, and is 97% similar in the C-terminal domain necessary for binding the GH promoter. However, the mouse cDNA encodes 16 zinc fingers, and sequences of rZn-15 pituitary cDNAs were the same as the mouse (m) Zn-16; the rat sequence in GenBank has a one nucleotide offset of a 17-bp segment in the finger V region. The mouse and corrected rat sequences contain four tandemly repeated fingers in the N-terminus, each separated by seven amino acids, typical of zinc finger proteins of the transcription factor IIIA-type. Analysis of mZn-16 expression by RT-PCR showed that the mRNA is produced at similar levels in normal and GH-deficient Ames dwarf (Prop-1<df–/–>) mouse pituitaries at postnatal day 1. Mouse Zn-16 mRNA also was detected by ribonuclease protection assay in the pre-somatotrophic mouse cell line GHFT1-5. The Zn-16 protein is bipartite in that the N-terminal half displays tandem spacing typical of most zinc finger proteins, while the C-terminal portion contains long linkers between fingers that cooperatively bind to a DNA response element. Expression in early postnatal pituitary and in pre-somatotrophic cells suggests that Zn-16 could play a role in pituitary development prior to somatotroph differentiation.

Can GHRH or GH secretagogues re-initiate pituitary GH pulsatility?

Can GHRH or GH secretagogues re-initiate pituitary GH pulsatility?

A variation of simple repeat sequence in the promoter region of the bovine growth hormone (bGH) gene in beef cattle is similar to water buffalo

Introduction Bovine growth hormone or somatotropin gene (bGH) maps to chromosome 19q17‐qter (Hediger et al. 1990) and consists of 5 exons (I–V) and 4 introns (A–D). The entire gene, including 5′ and 3′‐untranslated and signal peptide coding regions, covers a total of 2856 base pairs (Gordon et al. 1983). Growth hormone has wide biological activities including mammary development, lactogenic and growth‐promoting activities in cattle. Restriction fragment length polymorphisms (RFLPs) have been detected in intron C and exon V of the bGH gene (Hoj et al. 1993; Lucy et al. 1993) that is associated with milk yield, and it also seems to influence the breeding value for carcass gain in Simmental bulls (Schlee et al. 1994). Recently reported variants in the 5′ flanking region of the GH gene and in intron A were associated with potential binding sites for trans‐acting factors (Hecht and Geldermann 1996). Cis‐transcriptional elements and regulatory factors for GH gene expression have been identified in mammalian species: the pituitary‐specific factor PIT‐I (also called GHF‐I), the GHZ box (Lipkin et al. 1993) and the thyroid hormone (TH) (Tuggle and Trenkle 1996). Although the control of human and murine GH gene expression in the pituitary has been extensively studied, the details of GH gene regulation are not well understood in any species (Tuggle and Trenkle 1996). The level of expression of the bGH gene could be associated with some genetic polymorphism and consequently affect the performance of the animal. Therefore, to investigate the possible presence of polymorphisms in the promoter region of the bGH gene, we have genotyped different beef and dairy breeds, Bos taurus and Bos indicus and the water buffalo breeds, Bubalus bubalis.