An immunochemical and immunocytologic study of the increase in myometrial gap junctions (and connexin 43) in rats and humans during pregnancy.

Myometrial gap junctions are thought to play a necessary role in control of parturition. In this study we evaluated the presence of gap junctions in myometrial tissues with a specific antibody to the gap junction protein, connexin 43, with immunocytochemistry and immunoblots. Immunofluorescence of rat heart showed gap junctions were localized along the intercalated disks, but no change occurred during pregnancy. Fluorescent staining of rat myometria showed punctate staining of gap junctions between muscle cells during term and preterm birth, illustrating the tremendous increase in gap junctions during labor. Similarly, staining of human myometrial tissues was present in specimens from pregnant patients but absent in tissues from nonpregnant women. Immunoblots of myometrial tissues from rat and humans confirmed the existence of high levels of connexin 43 during term and preterm labor in rats and also during late pregnancy in humans.