GAP JUNCTIONAL PROTEINS, CONNEXIN-26, CONNEXIN-32, AND CONNEXIN-43 INSHEEP OVARIES THROUGHOUT THE ESTROUS-CYCLE

Ovarian follicles from days 13, 14, 15, and 16 and corpora lutea (CL) from days 2, 4, 8, 12, and 15 of the estrous cycle were evaluated for the presence of connexins by immunohistochemistry. In addition, CL fro m days 5, 10, and 15 of the estrous cycle were used for immunofluoresc ent detection of Cx43 followed by image analysis, and for Western immu noblot. In all tissues, staining for all connexins appeared punctate, indicating the presence of assembled gap junctions. Cx26 was present i n the ovarian surface epithelium, stroma, and blood vessels within the stroma and hilus, and in the CL. In healthy antral follicles, Cx26 wa s present only in the theca layer, whereas Cx43 was present in granulo sa and theca layers. In the majority of atretic follicles, connexins w ere not detected, but in 13% of the atretic follicles, Cx43 was presen t in the theca layer. Cx32 was detected in the blood vessels of ovaria n stroma and in the CL, and Cx43 was detected in the CL. Localization and/or expression of connexins depended on stage of luteal development . Western analysis demonstrated that expression of Cx32 in luteal tiss ues was similar across the estrous cycle. The area of positive stainin g for Cx43 and expression of Cx43 in luteal tissues decreased (p < 0.0 5) as the estrous cycle progressed. The pattern of expression of conne xins indicates that gap junctional proteins may be important in the re gulation of folliculogenesis and follicular atresia, as well as growth , differentiation, and regression of the CL.