Immunofluorescent localization of placental lactogen, chorionic gonadotrophin and its alpha and beta subunits in organ cultures of human placenta.

Localization of human placental lactogen (HPL), chorionic gonadotrophin (HCG) and its free alpha and beta subunits in mature and immature placental villi before and during organ culture was examined with an 'indirect' immunofluorescent technique using highly specific antisera. HPL fluorescence was strictly localized to the syncytiotrophoblast and the intensity of this fluorescence increased with gestational age and decreased with the time of culture. Undissociated HCG and HCG beta immunofluorescence was localized to the syncytiotrophoblast. Maximum intensity was observed in immature placentae and was not significantly affected by the duration of culture. However, irregular and patchy HCG and HCG beta immunofluorescence was seen in the cytotrophoblasts under conditions of extensive syncytiotrophoblastic damage. HCG alpha immunofluorescence was localized in the syncytiotrophoblast of immature placentae and was more intense in mature placentae. Beginning the third day of culture, HCG alpha fluorescence increased and was also present in the cytotrophoblast. On the basis of these observations and additional data, the possibility is discussed that cytotrophoblastic cells, better preserved than the syncytiotrophoblast in case of restricted energy and oxygen supply, may actively synthesize free HCG alpha, in addition to syncytiotrophoblastic production of this subunit. By contrast, HPL, undissociated HCG, and HCG beta are mainly or exclusively eleborated in the syncytiotrophoblastic layer.