[An immunohistochemical study of HCG and HPL on functional differentiation of human chorionic villi (author's...

The enzyme-labeled antibody method was used to examine the localized distribution and variation by gestation week of HCG and HPL in placenta of 44 cases. 1) HCG: Electron microscopy revealed HRP reaction products in cisterna and membrane of perinuclear spaces and endoplasmic reticulum of syncytial cell (S-cell), but not in surface of S-cell microvilli or in Langhans' cell (L-cell). HRP reaction products in S-cell were more appreciable during 5th-12th weeks of gestation in syncytial sprouts, junction of villi with decidua, and rami or ramuli chorii, and fewer after 12th weeks. 2) HPL: Electron microscopy revealed reaction products in nuclear membrane and membrane of endoplasmic reticulum and Golgi complex, but not in surface of S-cell microvilli or L-cell. Reaction products in S-cell were noted from 8th gestation week, and most appreciably in 16th-18th gestation weeks preceding peak HPL concentration in serum. This indicates HPL exists in S-cell in the from of Pre. Pro-HPL.