Melatonin potentially acts directly on swine ovary by modulating granulosa cell function and angiogenesis.

Melatonin exerts well known reproductive effects mainly acting on hypothalamic GnRH release. More recent data suggest that melatonin acts directly at ovarian level, even if, at present, these aspects have been only partly investigated. Swine follicular fluid contains melatonin and its concentration is significantly reduced during follicular growth. Therefore, present research was undertaken to study the effects of melatonin, used at physiological concentrations, on cultured swine granulosa cells collected from small (<3mm) and large (>5 mm) follicles on the main parameters of granulosa cell function such as proliferation, and steroidogenesis, namely estradiol 17β (E2) and progesterone (P4) production. Moreover, the effects of the examined melatonin concentrations were also considered on superoxide anion (O2-) and nitric oxide (NO) generation by swine granulosa cells. Finally, since angiogenesis is crucial for follicle growth, the effects of the indoleamine on new vessel growth were studied. Collected data indicate that the indoleamine interferes with cultured granulosa cell proliferation, steroidogenesis, specifically in term of P4 production and NO output. In addition, also the events of physiological follicular angiogenesis could be stimulated by melatonin as evidenced by the angiogenesis bioassay. Therefore, we suggest that physiological melatonin concentrations could be potentially involved in modulating locally swine ovarian follicle function.