Regulation of hormonal receptors of the hypothalamic-pituitary-gonadal axis by ghrelin in ovary of grass carp (Ctenopharyngodon idella)

Ghrelin has been well known as an orexigenic hormone that regulates appetite and energy metabolism in animals. Recent studies imply the regulatory function of ghrelin on ovary development, however, the mechanism about the effects of ghrelin on key hormonal receptors in ovary is far away from systematically understood. The present study aimed to analyze the tissue distribution of ghrelin and related genes and elucidate the regulation of ghrelin on key hormonal receptors in ovary of grass carp (Ctenopharyngodon idella). High expression of ghrelin and ghrelin O-acyltransferase (GOAT) was found in the ovary compared to heart, kidney, spleen, muscle, brain, liver, gill and intestine. To understand the regulatory function of ghrelin on ovarian development, the effects of ghrelin on the key hormone receptors participated in ovarian maturation were determined by ghrelin, acylghrelin and octanoic acid (substrate in the ghrelin acylation system) treatments with 1, 10 and 100 nM concentration. The in vivo study showed that all the 1, 10 and 100 nM ghrelin treatment stimulated folliclestimulating hormone receptor (FSHR) expression compared to the control. Estrogen Receptor-alpha (ER alpha) was depressed by 10 nM acyl-ghrelin compared to the control, while ER beta 1 and ER beta 2 could be inhibited by 1 nM and 10 nM octanoic acid treatment compared to the control, respectively. The present results for the first time provided novel information about the regulatory role of ghrelin on key hormonal receptors in ovarian of grass carp providing potential new ideas for cultivating of grass carp broodstock.