Relationship between ghrelin and estrogen in the ovary of pregnant sheep

Ghrelin, an endogenous ligand for the growth secretagogue receptor is predominantly produced in the stomach and an expression of ghrelin has recently been identified in placenta and ovary.
Therefore, we decited to measure ovarian ghrelin as quantitative and evaluate the correlation between ghrelin and estrogen during second half of ovine pregnancy.
The ovarian samples were collected from 40 pregnant sheep in 3, 3.5, 4, 4.5 and 5 months of pregnancy in a local abattoir. Follicles and active corpora lutea (CL) were dissected from surrounding tissues, separately. The samples were homogenized with phosphate buffer (0.1 M, pH 7.4) on liquid nitrogen to provide fluid samples. Ghrelin and estrogen concentrations were measured by ELISA method and expressed as milligram (mg) and picogram (pg) per mg of tissue protein, respectively.
There was a linear correlation between ghrelin and estrogen in ovarian follicles (r=0.97 and p=0.004), but not in CL. Follicular ghrelin significantly increased in 4, 4.5 and 5 months (p These results emphasize the role of ghrelin in the reproductive system and open a new window to future studies.