Submitted to: Domestic Animal Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2003
Publication Date: 11/25/2003
Citation: OUBRE, C.M., HONDT, E.D., MOORE, R.W., HARGIS, B.M., BERGHMAN, L.R. THE CHICKEN PITUITARY EXPRESSES AN OVOINHIBITOR-LIKE PROTEIN IN SUBPOPULATIONS OF SOME, BUT NOT ALL, HORMONE-PRODUCING CELL TYPES. DOMESTIC ANIMAL ENDOCRINOLOGY, pp 389-397, 2003. Interpretive Summary: An antibody developed against a protein extract from in the chicken bursa of Fabricius, the organ responsible for production of the cells which produce antibodies, was found to specifically bind a protein produced in hormone producing cells in chicken pituitaries, a hormone producing organ in the brain. This protein has been identified as chicken ovoinhibitor. The antibody to ovoinhibitor was observed to bind cells that produce growth hormone, luteinizing hormone, and opiomelanocortin, but did not bind to cells that produce prolactin, suggesting that production of ovoinhibitor is specific for certain hormone secreting cells. This is the first identification of ovoinhibitor in the pituitary of animals. By obtaining a better understanding of the function of ovoinhibitor in the pituitary, we may gain a better understand of the production and secretion of hormones.
Technical Abstract: Ovoinhibitor is a serine protease-inhibiting protein that was originally purified from egg whites. It is secreted by the oviduct under the control of estrogen and progesterone and it specifically inhibits serine proteinases such as trypsin and chymotrypsin. During recent attempts to raise monoclonal antibodies (Mabs) against chicken bursa of Fabricius proteins, one Mab was produced that specifically recognizes chicken ovoinhibitor. This was the first demonstration of ovoinhibitor in an avian immune organ. We presently report on the expression of an ovoinhibitor-like molecule by the pituitary of the chicken as revealed by immunocytochemistry and RT-PCR. Immunofluorescent dual staining experiments using the mouse anti-ovoinhibitor Mab in conjunction with polyclonal antibodies against various hypophysial hormones revealed partial co-localization of ovoinhibitor with growth hormone (GH), luteinizing hormone (LH), and pro-opiomelanocortin (POMC), in a subset of the respective hormone producing cells. By contrast, no co-localization with prolactin PRL or S-100 could be reliably demonstrated. While expression of ovalbumin-like serin protease inhibitors (serpins) has been previously reported in the rat pituitary, to our knowledge, this is the first report of a Kazal-type serpin in the vertebrate neuroendocrine system.