Cytochemical studies of the maternal surface of the syncytiotrophoblast of human early and term placenta.

Abstract

AbstractLight microscopic studies using a battery of basic dye stains combined with sialidase and hyaluronidase digestions indicated that the extensive basophilia of the maternal surface of the placental syncytium largely results from the presence of a non‐sulfated mucosubstance specifically identified as hyaluronic acid. Ultrastructural examination of dialyzed iron (DI) stained specimens revealed that DI‐positive filaments observed along the syncytial surface were removed by hyaluronidase digestion. Staining with the lectins, Concanavalin A or lentil bean hemagglutinin produced an intense and periodic pattern of staining that was not enzyme labile. Incubation of tissue sections in the enzyme solutions or control buffers allowed the lectins to penetrate the syncytial plasma membrane and stain material within the endoplasmic reticulum presumed to be human chorionic gonadotropin. The maternal surface exhibited essentially no reactivity for acid phosphatase but showed strong alkaline phosphatase activity with a periodic staining pattern. With each of the techniques used there was variability in the intensity of staining in different regions along the maternal surface, suggesting that functionally different zones may be identified cytochemically. Only minor differences were observed in the cytochemical reactivity of early compared with term placenta.