CONNEXIN-43 GAP FUNCTION PROTEIN EXPRESSION DURING FOLLICULAR DEVELOPMENT IN THE PORCINE OVARY

Connexin 43, a member of the highly conserved connexin family of gap j unction proteins, is expressed in the pig ovary, In other species, ova rian connexin 43 expression and phosphorylation are hormonally regulat ed. We characterized connexin 43 expression and phosphorylation in the ovaries of mature pigs during the estrous cycle and in prepubertal gi lts during follicular development induced by eCG (750 IU)/hCG (500 IU; 72 h later). Ovarian connexin 43 protein expression and phosphorylati on were examined by immunoblot analysis. Connexin 43 was localized to specific follicular cell types during development by immunofluorescenc e. While no change in total connexin 43 protein expression was seen du ring the cycle, connexin 43 phosphorylation was significantly higher ( p < 0.05) during the late follicular stage of the cycle than during th e early luteal and early to mid-follicular stages. In ovaries of eCG/h CG-primed prepubertal pigs, connexin 43 protein levels remained steady , while phosphorylation of the protein increased significantly at 72 h and 84 h after eCG treatment (p < 0.05), then declined to pretreatmen t levels by 96 h (24 h post-hCG administration). Immunoreactive connex in 43 was localized predominantly to granulosa cells of cyclic pigs an d eCG/hCG-primed prepubertal gilts. Follicular connexin 43 was highest between 60 h and 84 h after eCG and declined after hCG administration . Connexin 43 was not detected in morphologically atretic follicles, s troma, or vascular tissue of the ovary. This is the first evidence tha t porcine ovarian connexin 43 phosphorylation is differentially regula ted during follicular development. The results suggest that hormonally induced changes in connexin 43 phosphorylation may play a coordinatin g role in porcine follicular development.