Leptin modulates the expression of its receptors in the hypothalamic-pituitary-ovarian axis in a differential way

DI YORIO P; BILBAO M; PUSTOVRH C; PRESTIFILIPPO J; FALETTI A.

JOURNAL OF ENDOCRINOLOGY

Society for Endocrinology

Año: 2008 vol. 198 p. 355 - 366

0022-0795

To investigate the expression of leptin receptors (Ob-R) in the rat hypothalamus-pituitary-ovarian axis, immature rats were treated with eCG/hCG and Ob-R expression was evaluated by Western blot analysis. Ob-R expression increased 24 h after eCG administration in all the tissues assayed. In the hypothalamus, these levels immediately decreased to those obtained without treatment. In the pituitary, the Ob-R expression continued elevated 48 h after eCG administration, whereas the hCG injection did not modify these levels. Similar results were obtained with the ovarian long isoform. To assess the effect of leptin on its receptors, Ob-R was assessed in hypothalamus, pituitary and ovarian explants cultured in the presence or absence of leptin (0.3-500 ng.ml-1). In the hypothalamus, we found a biphasic effect: the Ob-R expression was either reduced or increased at low or high concentrations of leptin, respectively. Luteinizing hormone-releasing hormone secretion increased at 1 ng.ml-1. In the pituitary, Ob-R increased at 10 or 30 ng.ml-1of leptin, for the long and short isoforms, respectively. Leptin also induced an increase in luteinizing hormono release at 30 ng.ml-1. In the ovarian culture, the presence of leptin produced an increased in Ob-R expression at different ranges of concentrations and a dose-dependent biphasic effect on the progesterone production. In conclusion, all these results clearly suggest that leptin is able to modulate the expression of its own receptors in the reproductive axis in a differential way. Moreover, the positive or negative effect that leptin exerts on the ovulatory process may be dependent on this regulation.