EXPRESSION AND BIOLOGICAL ACTIVITY OF GHRELIN, OBESTATIN, AND LEPTIN IN DEFERENT DUCTS OF THE BULL AND RAM

Abstract

It is known that ghrelin, obestatin and leptin are involved in many biological processes such as appetite-energy regulation, growth hormone release and cell proliferation. In addition to these biological activities of in human and rodents, direct effects of these hormones on reproductive functions and regulation of smooth muscle contractions have gained importance in recent years. In mammals, gonadal functions are regulated by using a complex network of autocrine, paracrine and endocrine signals. The signals involved in the control of energy balance regulate reproductive functions by acting on different hypothalamic pituitary-gonadal axis. The underlying molecular mechanism of gonad is poorly understood and appears to be controlled on genetic, environmental, and hormonal factors. Ghrelin, obestatin and leptin, three recently discovered hormones, are especially coexpressed in endocrine cells. The purpose of this investigation was to examine the immunohistochemical expression and potential biological activity of bull and ram deferent ducts (DD) in relation to the tissue concentration of ghrelin, obestatin and leptin. Ghrelin, obestatin and leptin expression observed in the DD sections were restricted to the cytoplasm of the epithelial and muscle cells. Both ghrelin and leptin expressions were found in smooth muscle cells in muscular layer of DD and smooth muscle cells of blood vessels, and obestatin expression was found in the basal epithelial cells of the luminal epithelium. In conclusion, ghrelin, obestatin and leptin were expressed in varying concentrations in epithelial and muscle cells as well as blood vessels of the deferent ducts of both species. Given the multifunctional biological roles of these peptide hormones, we can suggest that these hormones function in the contraction and hypertrophy of smooth muscles, proliferation or apoptosis of epithelial and muscle cells in DD. Key words: deferent ducts; ghrelin; leptin; obestatin; ruminant; physiological function IZRAŽANJE IN BIOLOŠKA AKTIVNOST GRELINA, OBESTATINA IN LEPTINA V SEMENOVODU PRI BIKU IN OVNU Povzetek: Znano je, da so grelin, obestatin in leptin vključeni v številne biološke procese, kot so uravnavanje apetita, sproščanje rastnega hormona in spodbujanje delitev celic. Poleg omenjenih bioloških učinkov pri ljudeh in glodavcih so v zadnjih letih postali znani tudi njihovi neposredni učinki na delovanje spolnega sistema in uravnavanje kontrakcije gladkih mišic. Pri sesalcih je delovanje spolnih žlez uravnano z zapleteno mrežo avtokrinih, parakrinih in endokrinih sporočil. Sporočila, ki sodelujejo pri nadzoru energetskega ravnotežja v telesu pogosto vplivajo tudi na delovanje spolnega sistema z vplivom na hipotalamusno-hipofizno-spolno os. Osnovni molekularni mehanizem delovanja spolnih žlez je slabo raziskan, na njegovo delovanje pa vplivajo genetski, okoljski in hormonski dejavniki. Grelin, obestatin in leptin so trije hormoni, ki v telesu sodelujejo pri urejanju in ohranjanju energetskega ravnotežja. Namen raziskave je bil preučiti imunohistokemično izražanje in potencialno biološko aktivnost grelina, obestatina in leptina v semenovodu bikov in ovnov. Grelin, obestatin in leptin so izraženi v semenovodu in so bili omejeni na citoplazmo epitelijskih in mišičnih celic. Grelin in leptin sta bila izražena v gladkih mišičnih celicah mišične plasti semenovoda in gladkih mišičnih celicah krvnih žil. Obestatin je bil izražen v bazalnih epitelijskih celicah svetline semenovoda. Grelin, obestatin in leptin so torej izraženi v različnih koncentracijah v epitelnih in mišičnih celicah ter krvnih žilah v semenovodu pri biku in ovnu. Glede na raznolike biološke vloge teh peptidnih hormonov lahko predvidevamo, da ti hormoni morda sodelujejo pri krčenju in hipertrofiji gladkih mišic ter pri množenju ali apoptozi epitelijskih in mišičnih celic v semenovodu. Ključne besede: semenovod; grelin; leptin; obestatin; bik; oven; fiziološka funkcija