title: Localization of ghrelin and its receptor in the reproductive tract of Holstein heifers.
abstract: The aim of this experiment was to localize the mRNA and protein of ghrelin and its active receptor, growth hormone secretagogue 1A (GHS-R1A), within the reproductive tract of dairy cattle. Ghrelin is an orexigenic hormone that has been identified as a potent regulator of energy homeostasis. Recent evidence suggests that ghrelin may also serve as a metabolic signal to the reproductive tract. Ghrelin and GHS-R1A have been identified in the reproductive tract of several species, including humans, mice, and rats. However, ghrelin and GHS-R1A expression have not been described within bovine reproductive tissues. Therefore, the ampulla, isthmus, uterine body, corpus luteum, and follicles were harvested from 3 Holstein heifers (15.91±0.07 mo of age) immediately following exsanguination. Duodenum and hypothalamus were collected as positive controls for ghrelin and GHS-R1A, respectively. Tissues were fixed in 10% formalin and embedded in paraffin for microscopy. Additional samples were stored at -80°C for detection of mRNA. Ghrelin and GHS-R1A mRNA and protein were observed in all tissue types within the reproductive tract of dairy heifers; however, expression appeared to be cell specific. Furthermore, ghrelin protein appeared to be localized to the cytoplasm, whereas GHS-R1A protein was found on the plasma membrane. Within the reproductive tissues, ghrelin mRNA and protein were most abundantly expressed in the ampulla of the oviduct. Concentrations of GHS-R1A were lower than those of ghrelin but differed between tissues. This is one of the first studies to provide molecular evidence for the presence of ghrelin and GHS-R1A within the entire reproductive tract. However, implications for fertility remain to be determined.
authors.affiliation: Department of Animal Sciences, University of Arizona, Tucson 85721, USA.
authors.forename: S E
authors.initials: SE
authors.lastname: Deaver
authors.forename: P B
authors.initials: PB
authors.lastname: Hoyer
authors.forename: S M
authors.initials: SM
authors.lastname: Dial
authors.forename: M E
authors.initials: ME
authors.lastname: Field
authors.forename: R J
authors.initials: RJ
authors.lastname: Collier
authors.forename: M L
authors.initials: ML
authors.lastname: Rhoads
mesh_terms: D000818:Animals; D002417:Cattle; D003338:Corpus Luteum / Q000737:chemistry / Q000502:physiology; D004386:Duodenum / Q000737:chemistry; D005260:Female; D005455:Fluorescent Antibody Technique / Q000662:veterinary; D005836:Genitalia, Female / Q000737:chemistry* / Q000502:physiology; D054439:Ghrelin / Q000032:analysis / Q000502:physiology*; D007031:Hypothalamus / Q000737:chemistry; D006080:Ovarian Follicle / Q000737:chemistry / Q000502:physiology; D054440:Receptors, Ghrelin / Q000032:analysis / Q000502:physiology*; D014599:Uterus / Q000737:chemistry / Q000502:physiology
chemical_list: D054439:Ghrelin; D054440:Receptors, Ghrelin