title: The association between testicular ghrelin receptor mRNA and serum testosterone levels in immunocastrated boars.
abstract: Ghrelin, the endogenous ligand for the GH secretagogue receptor (GHS-R), has various functions. The expression of ghrelin and growth hormone secretagogue receptor type 1a (GHS-R1a) has been demonstrated in rat and human testis, and ghrelin also affects testosterone (T) secretion in vitro, suggesting a role for this molecule in the direct control of testis function. However, whether this signaling system is present in pig testis, and the association with serum T remains largely unexplored. In this study we investigated the relationship between serum T levels and ghrelin and GHS-R1a gene expression in the testes of intact and immunocastrated boars. Testicular tissue and serum samples were collected from seven intact boars and seven recombinant GnRH-I immunocastrated boars. GHS-R1a gene expression in the testis was higher in immunocastrated than intact boars (2.22 ± 0.71 vs. 0.53 ± 0.23; P<0.01). Mean serum T levels were markedly lower in immunocastrated than intact boars (0.40 ± 0.04 vs. 2.10 ± 0.94 ng/mL, P<0.01). Ghrelin gene expression in testis did not differ between both groups of boars. GHS-R1a gene expression was positively correlated with ghrelin gene expression (r = 0.68, P<0.001), but negatively correlated with serum T concentrations (r = -0.83, P<0.001). Overall, the existence of ghrelin and GHS-R1a gene expression in pig testis, and the increase in GHS-R1a gene expression in the testes and the inverse correlation with serum T in immunocastrated boars are highly suggestive of a role for ghrelin in the regulation of mammalian testicular function.
authors.affiliation: Department of Animal Veterinary Science, College of Animal Science and Technology, Anhui Agricultural University, Hefei, PR China.
authors.forename: Fugui
authors.initials: F
authors.lastname: Fang
authors.forename: Ya
authors.initials: Y
authors.lastname: Liu
authors.forename: Xijie
authors.initials: X
authors.lastname: Zhao
authors.forename: Yunsheng
authors.initials: Y
authors.lastname: Li
authors.forename: Yunhai
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000818:Animals; D054439:Ghrelin / Q000235:genetics / Q000378:metabolism*; D006651:Histocytochemistry; D008297:Male; D009919:Orchiectomy / Q000379:methods / Q000662:veterinary; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D054440:Receptors, Ghrelin / Q000235:genetics / Q000378:metabolism*; D018709:Statistics, Nonparametric; D013552:Swine / Q000378:metabolism*; D013737:Testis / Q000378:metabolism*; D013739:Testosterone / Q000097:blood* / Q000378:metabolism
chemical_list: D054439:Ghrelin; D012333:RNA, Messenger; D054440:Receptors, Ghrelin; D013739:Testosterone