Submitted to: Domestic Animal Endocrinology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/8/2002
Publication Date: 3/8/2002
Citation: CONNOR, E.E., ASHWELL, M.S., DAHL, G.E. CHARACTERIZATION AND EXPRESSION OF THE BOVINE GROWTH HORMONE-RELEASING HORMONE (GHRH) RECEPTOR. DOMESTIC ANIMAL ENDOCRINOLOGY. vol. 22, pp. 189-200, 2002. Interpretive Summary: In cattle, growth hormone (GH) production and release is stimulated by GH-releasing hormone (GHRH) The receptor for GHRH is expressed in the pituitary gland and also plays a role in GH regulation. The purpose of the present study was to clone and sequence the bovine pituitary GHRH receptor cDNA, to characterize the GHRH receptor gene, and to study changes in pituitary GHRH receptor expression in cattle treated with bovine somatotropin. In this study, we demonstrate that GHRH receptor is expressed in pituitary and hypothalamic tissues of cattle, but is not expressed in ovary or testis as is seen in rats. The predicted bovine GHRH receptor amino acid sequence is similar to the receptor in sheep, sharing 93% identity with the ovine sequence. The structure of the GHRH receptor gene is similar to that of the human gene. Unlike the GHRH receptor in rats, we demonstrate that treatment with somatotropin does not alter pituitary GHRH receptor expression in cattle.
Technical Abstract: The hypothalamic hormone, growth hormone-releasing hormone (GHRH) and its pituitary receptor are principal regulators of pituitary growth hormone (GH) synthesis and release. In the present study, we cloned and sequenced a complete bovine pituitary GHRH receptor cDNA in order to study its expression in cattle. The lengths of the exons in the bovine GHRH receptor rgene were determined by comparison of the cloned cDNA with genomic sequences obtained from a bovine genomic library clone. As in other species, the bovine cDNA sequence encodes a 423-amino acid protein containing seven hydrophobic domains characteristic of a G-protein coupled receptor. The predicted bovine amino acid sequence shares 93, 90, 89, 87 and 85% identity with the ovine, porcine, human, rat and mouse sequences, respectively. Expression of the receptor in bovine ileum, ovary, anterior pituitary, testis, hypothalamus, pancreas and liver was examined by RT-PCR. .Of those tissues examined, GHRH receptor expression was detected in the anterior pituitary gland and hypothalamus. To gain a better understanding of GHRH receptor gene regulation in ruminants, we examined the effect of bovine somatotropin (bST) treatment on pituitary GHRH receptor expression in dairy heifers using relative RT-PCR. Our results indicate that unlike in rodents, GH treatment does not alter pituitary GHRH receptor expression in cattle.