Inhibitory effect of leptin on the rat ovary during the ovulatory process.

RICCI, ANALÍA GABRIELA; DI YORIO, MARÍA PAULA; FALETTI, ALICIA GRACIELA

REPRODUCTION

BioScientifica

Año: 2006

1470-1626

The aims of this study were to investigate the negative action of leptin on some ovarian preovulatory factors during the ovulatory process and to assess whether leptin is able to alter the expression of its ovarian receptors. Immature rats primed with gonadotrophins were used to induce ovulation. Serum leptin concentration was diminished 4 h after hCG administration whereas the ovarian expression of leptin receptors, measured by Western Blot, was increased by the gonadotrophin treatment. Serum progesterone level, ovulation rate and ovarian prostaglandin E2 content were reduced in rats primed with eCG/hCG and treated with acute doses of leptin (5 doses of 5 µg each). These inhibitory effects were confirmed by in vitro studies, where the presence of leptin reduced the concentrations of progesterone, prostaglandin E2 and nitrites in the media of both ovarian explants and pre-ovulatory follicles cultures. We also investigated whether these negative effects were mediated by changes in the expression of the ovarian leptin receptors. Acute leptin treatment induced a swift increase on the ovarian leptin receptor expression 10 h after administration of hCG, but this result was not significant. This suggests that the inhibitory effect of leptin on the ovulatory process was not mediated by its receptors at ovarian level, at least at the concentrations assayed. In summary, the ovulatory process was significantly inhibited in response to an acute treatment with leptin, due, at least in part, to the direct or indirect impairment of some ovarian factors such as prostaglandins and nitric oxide.