Neuropeptide glutamic-isoleucine (NEI) specifically stimulates the secretory activity of gonadotrophs in primary cultures of female rat pituitary cells.
The neuropeptide EI (NEI) is derived from proMCH. It activates GnRH neurons, and has been shown to stimulate the LH release following intracerebroventricular administration in several experimental models. The aim of the present paper was to evaluate NEI actions on pituitary hormone secretion and cell morphology in vitro. Pituitary cells from female rats were treated with NEI for a wide range of concentrations (1-400x10(-8)M) and time periods (1-5h). The media were collected and LH, FSH, PRL, and GH measured by RIA. The interaction between NEI (1, 10 and 100x10(-8)M) and GnRH (0.1 and 1x10(-9)M) was also tested. Pituitary cells were harvested for electron microscopy, and the immunogold immunocytochemistry of LH was assayed after 2 and 4h of NEI incubation. NEI (100x10(-8)M) induced a significant LH secretion after 2h of stimulus, reaching a maximum response 4h later. A rapid and remarkable LH release was induced by NEI (400x10(-8)M) 1h after stimulus, attaining its highest level at 2h. However, PRL, GH and FSH were not affected. NEI provoked ultrastructural changes in the gonadotrophs, which showed accumulations of LH-immunoreactive granules near the plasma membrane and exocytotic images, while the other populations exhibited no changes. Although NEI (10x10(-8)M), caused no action when used alone, its co-incubation with GnRH (1x10(-9)M), promoted a slight but significant increase in LH. These results demonstrate that NEI acts at the pituitary level through a direct action on gonadotrophs, as well as through interaction with GnRH.
De Paul
Ana Lucía
AL
Centro de Microscopía Electrónica, Universidad Nacional de Córdoba, Ciudad Universitaria, Argentina. adepaul@cmefcm.uncor.edu
Attademo
Andrés Maximiliano
AM
Carón
Ruben Walter
RW
Soaje
Marta
M
Torres
Alicia Inés
AI
Jahn
Graciela Alma
GA
Celis
María Ester
ME
D000818:Animals; D002478:Cells, Cultured; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D052681:Gonadotrophs; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D013006:Growth Hormone / Q000378:metabolism; D007150:Immunohistochemistry; D007986:Luteinizing Hormone / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D009842:Oligopeptides / Q000494:pharmacology*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D011388:Prolactin / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar
D009842:Oligopeptides; C522850:neuropeptide EI; D007987:Gonadotropin-Releasing Hormone; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013006:Growth Hormone