Ultrastructural immuno-localization of IGF-1 and insulin receptors in rat pituitary culture. Evidence of a functional interaction between gonadotroph and lactotroph cells.

SILVINA GUTIÉRREZ ,; JORGE HUMBERTO MUKDSI ,; AGUSTÍN AOKI ,; ALICIA INÉS TORRES ,; ALEJANDRO PERALTA SOLER,; ELSA MARGARITA ORGNERO.

CELL AND TISSUE RESEARCH

Springer

Lugar: Heidelberg; Año: 2007 vol. 327 p. 121 - 132

0302-766X

In the present in vitro study of rat pituitary cells, the expression of receptors for insulin and insulin-like growth factor 1 (IGF-1) was investigated. A supplementary study was performed on morphological and proliferative changes in adenohypophyseal cells induced by insulin and IGF-1. The proliferation of lactotrophs was determinated by double immunostaining for BrdU and PRL. The 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 mM), an inhibitor of tyrosine kinase receptor, reduced the proliferation of lactotrophs elicited by the hormone and the growth factor.             The ultrastructural localization of the receptors for insulin and IGF-1 was investigated by immunocytochemistry of intact pituitary cells by applying the colloidal gold?protein A technique. Gonadotrophs expressed both receptors, and the specific labelling was restricted to this cell type. Electron microscopy observations of pituitary cell cultures incubated with insulin or IGF-1 revealed gonadotroph cells exhibiting the fine structural features of an 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 some factor synthesized by gonadotroph cells, besides stimulating the gonadotroph byosinthetic activity in a direct manner.