INCREASED LECTIN-BINDING CAPACITY OF TROPHOBLASTIC CELLS OF LATE DAY-5 RAT BLASTOCYSTS

The binding of lectins to the trophoblast of rat blastocysts has been studied using quantitative ultrastructural cytochemistry. Rat blastocy sts from early, mid and late d 5 of gestation were stained using bioti nylated lectins (Phytolacca americana [Phy am], fucose binding protein [FBP] and soybean agglutinin [SEA]) and a sensitive avidin-ferritin c ytochemical method, Electron micrographs of ferritin particles along t he membrane were processed to produce images for which grey scale leve ls could be established and the ferritin particles automatically count ed. The ferritin:membrane ratio was then calculated. Increased binding with Phy am (which detects short chain oligosaccharides) was found af ter midday of d 5, i.e. after hatching. Binding of FBP and SEA did not alter during the period studied. The increased concentration of oligo saccharides on the blastocyst surface membrane after hatching may have important implications for blastocyst attachment to the endometrium.