Immunocytochemical analysis of the expression of gap junction protein connexin 43 in the rat ovary.

The present immunocytochemical study examines in the rat ovary the pattern of expression of connexin 43 (Cx43), a subunit of gap junctions. Using a well-characterized specific antiserum against rat Cx43, immunoreactivity was not detected in the fetal ovary, i.e., prior to follicular formation. However, in the ovary of 20-day-old, 35-day-old, and adult rats, strong Cx43-immunoreactivity was associated with the cell borders of the follicular epithelium/granulosa cells of all developmental stages (primordial follicles, preantral and antral secondary follicles). In general, immunoreactivity of the granulosa cells of large antral follicles appeared more intense than the one of smaller follicles. Staining was also seen in oocytes (cytoplasmic staining). Theca cells of large antral follicles, but not of small follicles were immunoreactive. Immunoreactive interstitial cells were not seen in ovaries of 20- and 35-day-old animals, but staining in these cells was present in adult rats. In large follicles with signs of atresia, granulosa cells lacked Cx43-immunoreactivity, whereas Cx43-immunoreactivity in their theca interna strikingly increased. Corpora lutea in the cyclic adult rats were heterogeneously stained, with either no detectable immunoreactivity, staining of cell borders of most luteal cells, or with conspicuous staining of only a few cells. In the pregnant animals on gestation days (GD) 12, 14, and 17, all luteal cells stained strongly for Cx43 at the cell surface.(ABSTRACT TRUNCATED AT 250 WORDS)