Role of ghrelin in regulating rabbit ovarian function and the response to LH and IGF-I

The aim of these in vivo and in vitro studies was to examine the role of ghrelin in the control of plasma hormone concentrations, the proliferation, apoptosis and secretory activity of ovarian granulosa cells and the response of these cells to hormonal treatments. Female rabbits were injected with ghrelin (10 μg/animal/day for one week before ovulation induced by 25 IU PMSG and 0.25 IU LHRH). On the day of ovulation, blood samples were collected and analyzed for concentrations of progesterone (P₄), testosterone (T), estradiol (E₂), estrone-sulphate (ES), insulin-like growth factor I (IGF-I) and leptin (L) by RIA. Some control and ghrelin-treated animals were killed in the periovulatory period, their ovaries were weighed and granulosa cells were isolated and cultured for 2 d. Cell proliferation (expression of PCNA) and apoptosis (expression of TdT) were evaluated by immunocytochemistry and TUNEL respectively. Secretion of P₄, T, E₂, IGF-I, and prostaglandin F (PGF) by granulosa cells cultured with and without LH or IGF-I (1, 10 or 100 ng/ml medium) was assessed by RIA. The remaining control and treated animals were kept until parturition, while the number, viability and body weight of pups were recorded.