Expression of the orexigenic peptide ghrelin in the sheep ovary

Ghrelin has been implicated in the control of cell proliferation in reproductive tissue. Here, we provide evidence that both ghrelin mRNA and protein are present in ovarian follicles. Persistent expression of ghrelin was also demonstrated in sheep ovary throughout the estrous cycle and pregnancy. In fact, the relative mRNA levels of ghrelin varied depending on the stage of the cycle, with the highest expression during the development of the corpora lutea (CL) and minimal expression in the regressing CL. A similar pattern was seen during pregnancy. Dynamic changes in the profile of ghrelin expression during the estrous cycle and throughout pregnancy suggest a precise regulation of ovarian expression of ghrelin, which could represent a potential role for ghrelin in the regulation of luteal development. In conclusion, the presence of the ghrelin signaling system within the sheep ovary especially in the oocytes opens up the possibility of a potential regulatory role of this novel molecule in reproductive function.