This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Melamed, P. Articles by Yaron, Z. Search for Related Content PubMed PubMed Citation Articles by Melamed, P. Articles by Yaron, Z.

Possible Interactions between Gonadotrophs and Somatotrophs in the Pituitary of Tilapia: Apparent Roles for Insulin-Like Growth Factor I and Estradiol¹

Department of Zoology, Tel-Aviv University (P.M., G.G., H.R., Z.Y.), Ramat Aviv 69978, Israel; and the National Center for Mariculture, Israel Oceanographic and Limnological Research (H.R., A.E.), Eilat, Israel

Address all correspondence and requests for reprints to: Dr. Zvi Yaron, Department of Zoology, Tel Aviv University, Ramat Aviv 69978, Israel. E-mail: yaronz{at}post.tau.ac.il

The unique organization of the teleost pituitary, in which cells are grouped according to their characteristic hormone, makes this a suitable model for studying pituitary paracrine interactions. In a number of fish, including tilapia, there are variations in the circulating levels of the gonadotropins and GH, which are elevated during the reproductive season, suggesting interactions between the reproductive and growth axes. The aim of this study was to investigate paracrine interactions between the gonadotrophs and somatotrophs in the tilapia pituitary. Initially, dispersed pituitary cells were separated on a density gradient in which the gonadotrophs were found in the least dense fractions, and the somatotrophs were concentrated in the densest fraction. After 4 days in culture, cells in the least dense fractions showed characteristic cytoplasmic extensions not seen in the somatotrophs, which appeared small and failed to form aggregates; somatotrophs were found, however, attached to other non-GH cells. Staining of the nuclei with 4,6-diaminidino-2-phenyl-dihydrochloride revealed that the isolated somatotrophs had undergone nuclear condensation and fragmentation typical of apoptosis. Addition of either estradiol or human recombinant insulin-like growth factor I (IGF-I; 10 nM) to the somatotroph cultures increased the number of cell aggregates and reduced the number of condensed or fragmented nuclei. Immunocytochemical studies on pituitary sections revealed IGF-I immunoreactivity in regions of the proximal pars distalis that stain with gonadotropin IIß antisera and also in regions of the rostral pars distalis characteristic of corticotrophs; immunoreactive IGF-I was never seen in the region of the somatotrophs. Incubation of cells from the different fractions with testosterone (10 nM; 24 h) revealed that cells of the least dense fractions, which were rich in gonadotrophs, possessed aromatizing ability, which was absent in the somatotroph-enriched fraction. These results suggest that estradiol and IGF-I, both generated from cells other than the somatotrophs, may exert antiapoptotic effects and thus possibly control the size of this population of cells.

This article has been cited by other articles:

				J. Aizen, H. Kasuto, M. Golan, H. Zakay, and B. Levavi-Sivan Tilapia Follicle-Stimulating Hormone (FSH): Immunochemistry, Stimulation by Gonadotropin-Releasing Hormone, and Effect of Biologically Active Recombinant FSH on Steroid Secretion Biol Reprod, April 1, 2007; 76(4): 692 - 700. [Abstract] [Full Text] [PDF]

				Y Kazeto and J M Trant Molecular biology of channel catfish brain cytochrome P450 aromatase (CYP19A2): cloning, preovulatory induction of gene expression, hormonal gene regulation and analysis of promoter region J. Mol. Endocrinol., December 1, 2005; 35(3): 571 - 583. [Abstract] [Full Text] [PDF]

				J. Schwartz Intercellular Communication in the Anterior Pituitary Endocr. Rev., October 1, 2000; 21(5): 488 - 513. [Abstract] [Full Text]

				D. M. Baker, B. Davies, W. W. Dickhoff, and P. Swanson Insulin-Like Growth Factor I Increases Follicle-Stimulating Hormone (FSH) Content and Gonadotropin-Releasing Hormone-Stimulated FSH Release from Coho Salmon Pituitary Cells In Vitro Biol Reprod, September 1, 2000; 63(3): 865 - 871. [Abstract] [Full Text]

				H. A. Hofmann and R. D. Fernald Social Status Controls Somatostatin Neuron Size and Growth J. Neurosci., June 15, 2000; 20(12): 4740 - 4744. [Abstract] [Full Text] [PDF]

				S. Windeatt, T. D. Southgate, R. A. Dewey, F. Bolognani, M. J. Perone, A. T. Larregina, T. C. Maleniak, I. D. Morris, R. G. Goya, D. Klatzmann, et al. Adenovirus-Mediated Herpes Simplex Virus Type-1 Thymidine Kinase Gene Therapy Suppresses Oestrogen-Induced Pituitary Prolactinomas J. Clin. Endocrinol. Metab., March 1, 2000; 85(3): 1296 - 1305. [Abstract] [Full Text]