Neuropeptide Glutamic-Isoleucine (NEI) specifically stimulates the secretory activity of gonadotrophs in primary cultures of female rat pituitary cells

DE PAUL, A.L.; ATTADEMO, A.M.; CARON, R.; SOAJE, M.; TORRES, A.I.; JAHN, G.A.; CELIS, M.E.

PEPTIDES

ELSEVIER SCIENCE INC

Año: 2009 vol. 30 p. 2081 - 2087

0196-9781

Abstract Neuropeptide EI (NEI) is derived from proMCH , activates GnRH neurons and its intracerebroventricular administration stimulates LH release 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 in a wide range of concentrations (20 ng/ml - 6 µg/ml) and times (1 - 5 h). Media were collected and LH, FSH, PRL, and GH measured by RIA. The interaction between NEI (20 - 2 000 ng/ml) and GnRH (0.1 and 1 ng/ml) was also tested. Pituitary cells were harvested for electron microscopy and the immunogold immunocytochemistry of LH was assayed after two and four hours of NEI incubation. NEI (2 µg/ml) induced a significant LH secretion after 2 h of stimulus, reaching a maximum response after 4 h. NEI (6 µg/ml) induced a rapid and remarkable LH release 1h after stimulus, attaining the highest level at 2 h. PRL, GH and FSH were not affected. NEI provoked ultrastructural changes in gonadotrophs, which showed accumulation of LH-immunoreactive granules near the plasma membrane and exocytotic images, while the other populations exhibited no changes. Co-incubation with a concentration of NEI (200 ng/ml) without action by itself, with GnRH (1 ng/ml), 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 interacting with GnRH.