Immunohistochemical localization of relaxin, prolactin and prostaglandin synthase in human amnion, chorion and decidua.

Relaxin, prolactin and prostaglandin synthase were localized by the avidin-biotin immunoglucose oxidase method in human amnion, chorion and decidua. Specimens from ten normal spontaneous deliveries and four elective Caesarean section deliveries with no labour were compared. Relaxin was found more consistently in the cells of the chorionic cytotrophoblast than in the cells of the parietal decidua adherent to the fetal membranes. Only half the tissues after spontaneous delivery contained positive relaxin-stained cells, whereas all the tissues from elective Caesarean sections contained cells positively stained with antiserum to relaxin. In both series of tissues prolactin was localized predominantly in the parietal decidual cells and was very infrequently found in the chorionic cytotrophoblast. Polyclonal antiserum to prostaglandin synthase was used to identify those cells producing prostaglandin in amnion, chorion and decidua. The cells of the amnion and chorion showed positive immunolocalization with no differences between tissues collected before or after labour. Double immunostaining using avidin-biotin immunoperoxidase for prolactin, followed by avidin-biotin immunoglucose oxidase for prostaglandin synthase, produced identical results in the same series of tissues examined with the single-staining method.