Action of Leptin on Gonadotrope Cells in Podarcis sicula Pituitary Gland

Leptin, the protein product of the ob gene, plays an important role in the regulation of food intake and energy balance. It has also a function as neuroendocrine hormone and is involved in controlling gonadotropin secretion by stimulatory hypothalamic and pituitary actions. Leptin has been found in all major taxa but few is known on its action in the reptile. In the present work we have analysed the action of intraperitoneal injection of recombinant human leptin, at different concentrations higher than their physiological values, on the gonadotrope (GTH) cells in the pituitary gland of Podarcis sicula female lizard. The study was performed during the period of reproductive quiescence and the cells were analysed by an immunohistochemical study. We have observed that in these reptiles, exposed at low doses of leptin, FSH and LH cells showed a decrease in immunoreactivity. At high doses, the same cells indeed appeared markedly immunoreactive and numerous. The data are indicative of a role of leptin on the modulation of the cellular activity of gonadotrope cells in P. sicula pituitary gland. This action appears dose-dependent and is similar to that already reported in mammals with interesting implications in evolutionary biology to study.