[Polarization optical investigations for the demonstration of a "sialomucin coat" at the surface of the chorionic epithelium of the rabbit placenta in relation to the stage of pregnancy].

Histological, histochemical, fluorescence optical and polarization microscopical investigations were performed in 53 placentas of rabbits from the 10th to the 35th day of pregnancy. A "sialomucin coat" could be demonstrated in all cases at the maternal surface of the metabolic barrier of the placenta. Polarization optical measurements after association with N,N'-diethylpseudoisocyanine chloride showed a lower content of sialic acid at the surface of the trophoblast in postmature placentas of rabbits in comparison to normal mature placentas. The immunological function of the placental barrier is discussed with respect to maturity.