Relationship between ghrelin and estrogen in the ovary of pregnant sheep

Background: 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. objectives: therefore, we decited to measure ovarian ghrelin as quantitative and evaluate the correlation between ghrelin and estrogen during second half of ovine pregnancy. methods: 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. results: 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<0.001) but cl ghrelin significantly decreased in the 4.5 month of ovine pregnancy (p<0.01). estrogen concentration was also significantly higher in 4-5 months of pregnancy in ovarian follicles (p<0.001) but potent cl indicated higher estrogen level only in the 5th month of pregnancy (p<0.001). conclusions: these results emphasize the role of ghrelin in the reproductive system and open a new window to future studies.