Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) play key roles in vertebrate gametogenesis and steroidogenesis. They are mainly synthesized in the pituitary gland. While investigating the ontogeny of FSH and LH cells in the cichlid fish Cichlasoma dimerus by immunohistochemistry (IHC), we unexpectedly found immunoreactive neurons in the preoptic area, sending their projections through different brain areas and neurohypophysis. Our previous work using Western blot and IHC techniques applied to the adult brain confirmed these findings. To further demonstrate the extrapituitary expression of these hormones, we performed RT-PCR detecting sequences coding for β-FSH and β-LH subunits in the C. dimerus pituitary and brain (preoptic-hypothalamic area). The expression of these transcripts in both organs was consistent with their peptide expression showing a high sequence homology when compared with other phylogenetically related fish. An individual pituitary in vitro culture system was utilized to study the possible modulatory effect of brain-derived gonadotropins on pituitary hormone secretion. Pituitary explants were cultured with different concentrations of LH or FSH, and the culture media were analyzed by Western blot. Exogenous LH produced a dose-dependent increase in pituitary β-LH, β-FSH and somatolactin (SL) releases. No effect was observed on growth hormone (GH). The effect on prolactin (PRL) was not consistent among treatments. Exogenous FSH produced an inhibition in β-LH release, dose-dependent increases in β-FSH and SL releases, and no effect on PRL and GH releases. These findings support the concept of regulation of pituitary trophic hormones by brain-derived gonadotropins.

Keywords:
Reproduction, Cichlids, Pituitary culture, Immunohistochemistry
1.
Croxatto H, Arrau J, Croxatto H: Luteinizing hormone-like activity in human median eminence extracts. Nature 1964;204:584–585.
2.
Emanuele N, Oslapas R, Connick E, Kirsteins L, Lawrence AM: Hypothalamic LH may play a role in control of pituitary LH release. Neuroendocrinology 1981;33:12–17.
3.
Hostetter G, Gallo RV, Brownfield MS: Presence of immunoreactive luteinizing hormone in the rat forebrain. Neuroendocrinology 1981;33:241–245.
4.
Chu C, Gao G, Huang W: A study on co-localization of FSH and its receptor in rat hippocampus. J Mol Histol 2008;39:49–55.
5.
Hojvat S, Emanuele N, Baker G, Connick E, Kirsteins L, Lawrence AM: Growth hormone (GH), thyroid-stimulating hormone (TSH), and luteinizing hormone (LH)-like peptides in the rodent brain: non-parallel ontogenic development with pituitary counterparts. Dev Brain Res 1982;256:427–434.
6.
Pacold ST, Kirsteins L, Hojvat S, Lawrence AM: Biologically active pituitary hormones in the rat brain amygdaloid nucleus. Science 1978;199:804–806.
7.
Mousa MA, Mousa SA: Immunocytochemical study on the localization and distribution of the somatolactin cells in the pituitary gland and the brain of Oreochromis niloticus (Teleostei, Cichlidae). Gen Comp Endocrinol 1999;113:197–211.
8.
Parhar IS, Iwata M, Pfaff DW, Schwanzel-Fukuda M: Embryonic development of gonadotropin-releasing hormone neurons in the sockeye salmon. J Comp Neurol 1995;362:256–270.
9.
Parhar IS, Soga T, Ogawa S, Sakuma Y: FSH and LH-β subunits in the preoptic nucleus: ontogenic expression in teleost. Gen Comp Endocrinol 2003;132:369–378.
10.
Sower SA, Takahashi A, Nozaki M, Gorbman A, Youson JH, Joss J, Kawauchi H: A novel glycoprotein in the olfactory and pituitary systems of larval and adult lampreys. Endocrinology 1995;136:349–356.
11.
Pandolfi M, Lo Nostro FL, Shimizu A, Pozzi AG, Meijide FJ, Vazquez GR, Maggese MC: Identification of immunoreactive FSH and LH cells in the cichlid fish Cichlasoma dimerus during the ontogeny and sexual differentiation. Anat Embryol 2006;211:355–365.
12.
Ito R, Abe SI: FSH-initiated differentiation of newt spermatogonia to primary spermatocytes in germ-somatic cell reaggregates cultured within a collagen matrix. Int J Dev Biol 1999;43:111–116.
13.
Shimizu A, Yamashita M: Purification of mummichog (Fundulus heteroclitus) gonadotropins and their subunits, using an immunochemical assay with antisera raised against synthetic peptides. Gen Comp Endocrinol 2002;125:79–91.
14.
Yazawa T, Yamamoto T, Jin Y, Abe S: Follicle-stimulating hormone is indispensable for the last spermatogonial mitosis preceding meiosis initiation in newts (Cynops pyrrhogaster). Biol Reprod 2002;66:14–20.
15.
Canepa MM, Pandolfi M, Maggese MC, Vissio PG: Involvement of pars intermedia hormones (MCH, αMSH and somatolactin) during background adaptation in the cichlid fish Cichlasoma dimerus. J Exp Zool 2006;305:410–419.
16.
Pandolfi M, Paz DA, Maggese MC, Meijide FJ, Vissio PG: Immunocytochemical localization of different cell types in the adenohypophysis of Cichlasoma dimerus (Teleostei, Perciformes). Biocell 2001;25:35–42.
17.
Pandolfi M, Paz DA, Maggese MC, Ravaglia MA, Vissio PG: Ontogeny of immunoreactive somatolactin, prolactin and growth hormone secretory cells in the developing pituitary gland of Cichlasoma dimerus (Teleostei, Cichlidae). Anat Embryol 2001;203:461–468.
18.
Canepa MM, Pozzi AG, Astola A, Maggese MC, Vissio PG: Effect of salmon melanin-concentrating hormone and mammalian gonadotrophin releasing hormone on somatolactin release in pituitary culture of Cichlasoma dimerus. Cell Tissue Res 2008, in press.
19.
Rosenfeld H, Levavi-Sivan B, Gur G, Melamed P, Meiri I, Yaron Z, Elizur A: Characterization of tilapia FSHbeta gene and analysis of its 5′ flanking region. Comp Biochem Physiol B 2001;129:389–398.
20.
Yaron Z, Gur G, Melamed P, Rosenfeld H, Levavi-Sivan B, Elizur A: Regulation of gonadotropin subunit genes in tilapia. Comp Biochem Physiol B Biochem Mol Biol 2001;129:489–502.
21.
Saga T, Oota Y, Nozaki M, Swanson P: Salmonid pituitary gonadotrophs. III. Chronological appearance of GTH I and other adenohypophysial hormones in the pituitary of the developing rainbow trout (Oncorhynchus mykiss irideus). Gen Comp Endocrinol 1993;92:233–241.
22.
Vischer HF, Bogerd J: Cloning and functional characterization of a gonadal luteinizing hormone receptor complementary DNA from the African catfish (Clarius gariepinus). Biol Reprod 2003;68:262–271.
23.
Kumar RS, Ijiri S, Trant JM: Molecular biology of the channel catfish gonadotropins receptors: 2. Complementary DNA cloning, functional expression, and seasonal gene expression of the follicle-stimulating hormone receptor. Biol Reprod 2001;65:710–718.
24.
Oba Y, Hirai T, Yohiura Y, Yoshikuni M, Kawauchi H, Nagahama Y: The duality of fish gonadotropins receptors: cloning and characterization of a second gonadotropin receptor cDNA expressed in the ovary and testis of amago salmon (Oncorhynchus rhodurus). Biochem Biophys Res Commun 1999;265:366–371.
25.
Demski LS, Sloan HE: A direct magnocellular-preopticospinal pathway in goldfish: implications for control of sex behavior. Neurosci Lett 1985;55:283–288.
26.
Foran CM, Bass AH: Preoptic GnRH and AVT: axes for sexual plasticity in teleosts fish. Gen Comp Endocrinol 1999;116:141–152.
27.
Pandolfi M, Muñoz Cueto JA, Lo Nostro FL, Downs JL, Paz DA, Maggese MC, Urbanski HF: GnRH systems of Cichlasoma dimerus (Perciformes, Cichlidae) revisited: a localization and developmental study using antibodies and riboprobes to the GnRH-associated peptides. Cell Tissue Res 2005;321:219–232.
28.
Molitch M, Edmonds M, Jones EE, Odell WD: Short-loop feedback control of luteinizing hormone in the rabbit. Am J Physiol 1976;230:907–910.
29.
Wong T, Zohar Y: Novel expression of gonadotropin subunit genes in oocytes of the gilthead seabream (Sparus aurata). Endocrinology 2004;145:5210–5220.
© 2008 S. Karger AG, Basel
2008
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.