Ultrastructural immunolocalization of IGF-1 and insulin receptors in rat pituitary culture: evidence of a functional interaction between gonadotroph and lactotroph cells

• Published in: Cell and tissue research 2007-01, Vol.327 (1), p.121-132
• Main Authors: Gutiérrez, Silvina, Mukdsi, Jorge Humberto, Aoki, Agustín, Torres, Alicia Inés, Soler, Alejandro Peralta, Orgnero, Elsa Margarita
• Format: Article
• Language: English
• Subjects: Animals; Cell Count; Cell culture; Cell Proliferation; Cells, Cultured; Cellular biology; DNA - biosynthesis; Dose-Response Relationship, Drug; Drug Combinations; Female; Fluorescent Antibody Technique, Direct; Gonadotrophs - cytology; Gonadotrophs - metabolism; Gonadotrophs - ultrastructure; Hormones; Immunoenzyme Techniques; Insulin; Insulin - pharmacology; Insulin-Like Growth Factor I - pharmacology; Lactotrophs - cytology; Lactotrophs - metabolism; Lactotrophs - ultrastructure; Microscopy, Electron, Transmission - methods; Pituitary gland; Pituitary Gland, Anterior - metabolism; Pituitary Gland, Anterior - ultrastructure; Rats; Rats, Wistar; Receptor, IGF Type 1 - metabolism; Receptor, IGF Type 1 - ultrastructure; Receptor, Insulin - metabolism; Receptor, Insulin - ultrastructure; Rodents
• ISSN: 0302-766X; 1432-0878
• DOI: 10.1007/s00441-006-0283-4

We have investigated the expression of receptors for insulin and insulin-like growth factor 1 (IGF-1) in rat pituitary cells in vitro and examined the morphological and proliferative changes induced in adenohypophyseal cells by insulin and IGF-1. The proliferation of lactotrophs was determined by double-immunostaining for bromodeoxyuridine and prolactin. Incubation with insulin (10, 100 or 1000 ng/ml) or IGF-1 (5, 30 or 100 ng/ml) for 48 or 72 h significantly increased the number of lactotrophs undergoing mitosis. Co-incubation of insulin or IGF-1 with genistein (25 microM), an inhibitor of the tyrosine kinase receptor, reduced the proliferation of lactotrophs elicited by the hormone and the growth factor. The receptors for insulin and IGF-1 were localized in intact pituitary cells by ultrastructural immunocytochemistry with the colloidal gold-protein A technique. Gonadotrophs expressed both receptors, specific labelling being restricted to this cell type. Electron-microscopical observations of pituitary cell cultures incubated with insulin or IGF-1 revealed gonadotroph cells exhibiting the fine-structural features of enhanced protein synthetic activity. These findings suggest that both insulin and IGF-1 are able to induce the proliferation of lactotrophs through an indirect mechanism mediated by a factor synthesized by gonadotroph cells, in addition to stimulating the biosynthetic activity of the gonadotroph in a direct manner.