Expression of gap junctional connexins 26, 32, and 43 mRNA in ovarian preovulatory follicles and corpora lutea in sheep.

The objective of the current study was to evaluate the expression of connexins (Cx)26, Cx32, and Cx43 mRNA in granulosa and theca cells during the peri-ovulatory period (experiment 1) and in the corpus luteum (CL) during the estrous cycle (experiment 2) and during prostaglandin F2alpha (PGF)-induced luteal regression (experiment 3) in FSH-treated ewes. In experiment 1, Cx26, Cx32, and Cx43 mRNA was expressed in granulosa and theca cells, and expression of Cx32 and Cx43 mRNA, but not Cx26, was greater (p<0.001) in granulosa than in theca cells throughout the peri-ovulatory period. Expression of Cx43 mRNA in granulosa and theca cells decreased (p<0.01) 24 h after hCG treatment. In experiment 2, expression of Cx26 mRNA in the CL tended to be greater (p<0.06) on day 10 than on days 5 or 15, but expression of Cx43 mRNA was greater (p<0.01) on day 5 than on days 10 and 15 of the estrous cycle. In experiment 3, expression of Cx26, but not Cx32 or Cx43 mRNA decreased (p<0.001) during PGF-induced luteal regression. In all 3 experiments, expression of Cx32 mRNA was much less than Cx26 and Cx43 mRNA. Moreover, Cx32 mRNA expression was unchanged during the peri-ovulatory period or during several stages of luteal development and PGF-induced regression of the CL. Thus, we have shown that the mRNA expression pattern of Cx26 and Cx43 changes during peri-ovulatory period and during several stages of the luteal development. This suggests that Cx26 and Cx43 play a role in ovarian tissue remodeling during the critical time around ovulation and throughout luteal tissue growth, differentiation, and regression in sheep.