LECTIN HISTOCHEMISTRY OF RAT PLACENTAL TISSUES

Lectin binding of rat trophoblast subpopulations was examined at days 10, 12 and 15 of gestation. Biotinylated lectins, specific for a range of carbohydrates, were applied to paraffin wax embedded tissues. At d ay 10 of pregnancy, a wide and similar range of lectins reacted with e ctoplacental cone and giant cells: chorionic lamina was relatively unr eactive except with wheat germ agglutinin. At days 12 and 15, the rang e of lectins reacting with the placental labyrinth was relatively rest ricted. Spongiotrophoblast at day 12 showed lectin reactivity similar to that of ectoplacental cone cells but at day 15 the reaction pattern indicated loss of N-acetylgalactosamine residues in the large, glycog en-rich cells. Trophoblastic giant cells also showed wide lectin react ivity: some reacted only with cytoplasmic components whilst others sho wed pericellular reactivity. Varying lectin reactivity of giant cells in different regions of the placenta suggests functional differences. There was reduced lectin reactivity of endovascular trophoblast at day 15, compared with day 12 of pregnancy, which may reflect altered inva sive potential associated with loss of sialic acid and N-acetylgalacto samine residues. The pattern of lectin reactivity suggests that ectopl acental cells, as well as giving rise to giant cells, may also contrib ute to spongiotrophoblast and to endovascular trophoblast. (C) 1996 W. B. Saunders Company Ltd