Expression and localization of ghrelin and its receptor in ovarian follicles during different stages of development and the modulatory effect of ghrelin on granulosa cells function in buffalo

Highlight
• Ghreiln and GHS-R1a expression increased with increase in follicle size.
• Both factors localized in granulosa and theca cells of ovarian follicle.
• Ghrelin have inhibitory effect on estradiol secretion from cultured granulosa cells.
• Ghrelin stimulate cell proliferation and inhibit apoptosis on cultured granulosa cell.

Ghrelin, a hormone predominantly found in the stomach, was recently described as a factor that controls female reproductive function. The aim of our study was to investigate the expression and localization of ghrelin and its active receptor, growth hormone secretagogue receptor type 1a (GHS-R1a) in buffalo ovarian follicles of different follicular size and to investigate role of ghrelin on estradiol (E2) secretion, aromatase (CYP19A1), proliferating cell nuclear antigen (PCNA) and apoptosis regulator Bax gene expression on granulosa cell culture. Using real time PCR and western blot, we measured gene and protein expression of examined factors. Localization was done with immunofluorescence method. Expression of ghrelin increased with follicle size with significantly highest in dominant or pre-ovulatory follicle (P < 0.05). Expression of GHS-R1a was comparable in medium and large follicle but was higher than small follicles (P < 0.05). Both the factors were localized in granulosa and theca cells. Pattern of intensity of immunofluorescence was similar with mRNA and protein expression. In the in vitro study granulosa cells (GCs) were cultured and treated with ghrelin each at 1, 10 and 100 ng/ml concentrations for two days after obtaining 75–80 per cent confluence. Ghrelin treatment significantly (P < 0.05) inhibited E2 secretion, CYP19A1 expression, apoptosis and promoted cell proliferation. In conclusion, this study provides novel evidence for the presence of ghrelin and receptor GHS-R1a in ovarian follilcles and modulatory role of ghrelin on granulosa cell function in buffalo.