Comparative immunohistochemical distribution of connexin 37 and connexin 43 throughout folliculogenesis in the bovine ovary

Among gap junctional proteins previously identified in the mouse ovary, con nexins (Cx) Cx37 and Cx43 appeared to be essential for normal follicular gr owth. The aim of this work was to detect Cx37 expression in the bovine ovar y, then to quantify and compare its follicular distribution pattern with th at of Cx43 using quantitative analysis of immunofluorescently labeled ovary sections viewed with a confocal laser scanning microscope. Cx37 immunoreac tivity was detected in bovine ovarian follicles and was predominantly local ized at preantral stages. Unlike follicular Cx43 expression which was restr icted to granulosa cells, Cx37 staining was observed in both oocyte and gra nulosa cell compartments. While no changes were seen during early follicula r growth, the level of Cx37 expression decreased significantly at the onset of antral cavity formation (PI 0.01). On the contrary to what was found fo r Cx37, Cx43 was weakly expressed in preantral follicles. Concomitant with antrum formation, the level of Cx43 expression increased significantly (P l ess than or equal to 0.01). A further increase was correlated with antral f ollicular size (P less than or equal to 0.01). Cx43 immunoreactivity declin ed significantly in morphologically atretic follicles (PI 0.01). A comparat ive analysis showed that Cx37 and Cx43 expression patterns were differentia lly regulated and could reflect specific physiological roles for each gap j unction protein throughout folliculogenesis in cow, (C) 2000 Wiley-Liss, In c.