Ultrastructural immunolocalization of IGF-1 and insulin receptors in rat pituitary culture: evidence of a functional interaction between gonadotroph and lactotroph cells.
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.
Gutiérrez
Silvina
S
Centro de Microscopía Electrónica, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Haya de la Torre esq. E. Barros, X5000HRA Córdoba, Argentina.
Mukdsi
Jorge Humberto
JH
Aoki
Agustín
A
Torres
Alicia Inés
AI
Soler
Alejandro Peralta
AP
Orgnero
Elsa Margarita
EM
D000818:Animals; D002452:Cell Count; D049109:Cell Proliferation; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D005260:Female; D019085:Fluorescent Antibody Technique, Direct; D052681:Gonadotrophs / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D007124:Immunoenzyme Techniques; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D052682:Lactotrophs / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission / Q000379:methods*; D010903:Pituitary Gland, Anterior / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D017526:Receptor, IGF Type 1 / Q000378:metabolism* / Q000648:ultrastructure; D011972:Receptor, Insulin / Q000378:metabolism* / Q000648:ultrastructure
D004338:Drug Combinations; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D004247:DNA; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin