A protective role of resveratrol against the effects of immobilization stress in corpora lutea of mice in early pregnancy

In the present study, we aimed to investigate a protective role for resveratrol against the effects of immobilization stress on corpora lutea (CL) of mice in early pregnancy. A total of 45 early-pregnant mice were divided into no immobilization stress (NIS) group, immobilization stress (IS) group, and immobilization and resveratrol treatment (IS+RES) group (n=15). Mice were immobilized in plastic tubes (50 mL) for 3 h per day during day 1 to 7 of pregnancy. In the IS+RES group, 5 mg kg−1 d−1 of resveratrol was administered just prior to application of stress. We analyzed apoptotic activity in CL by Western blotting analysis (WB), transmission electron microscopy (TEM), and immunohistochemistry (IHC). Serum progesterone levels were examined with radioimmunoassay (RIA). IHC results showed that the intensity of positive staining for Bax was increased, and for Bcl-2 was decreased in CL after IS, while resveratrol treatment reversed the positive staining for Bax and Bcl-2. WB revealed that immobilization stress up-regulated the expression of Bax and caspase-9, and down-regulated Bcl-2 expression, while resveratrol treatment attenuated the effects of immobilization stress on the expression of Bax, Bcl-2 and caspase-9. According to our TEM results, apoptosis as defined by chromatin condensation was found in CL after immobilization stress, while resveratrol inhibited the apoptosis. We also demonstrated that immobilization stress decreased progesterone concentrations and ovarian expression of StAR, while resveratrol restored the concentrations of progesterone and expression of StAR back to normal. These results indicated that immobilization stress induced luteal regression while resveratrol inhibited luteal regression, suggesting that resveratrol plays a protective role on corpora lutea of mice during early pregnancy.