Inhibition of implantation of hamster embryos by lectins

In order to test their effects on implantation, lectins (Con A and WGA) were infused into one horn of the uterus of each female hamster aged between 10 and 14 weeks at day 3 of pregnancy (D3). Con A was given to three groups of 10 animals each at dosages of 100, 200 and 400 micrograms/10 microliter normal saline (NS)/animal, and WGA to four groups of animals at dosages of 20, 50, 100 and 200/10 microliter NS/animal. Control groups consisted of untreated animals and animals treated with saline. On D8, laparotomy was performed and the number of fetuses were counted. In untreated and NS-treated groups the number of fetuses were 6.9 and 6.8 per horn, which were not significantly different. In Con A-treated groups, at dosages of 100, 200 and 400 micrograms the number of fetuses were 2.2, 2.5 and 2.1 per horn, respectively. By contrast, in WGA-treated groups no implantation was detected, except at the dosage of 20 micrograms, in which 1.1 fetuses per horn was observed. To study the mechanism of inhibition, another three groups of animals were similarly treated with NS, 100 micrograms Con A and 50 micrograms WGA/10 microliter NS/animal, respectively. On D4 at 1300-1400 h, uterine lumens were flushed to collect unimplanted blastocysts. No blastocyst was found in NS- and Con A-treated groups, whereas 6.2 blastocysts with complete zona pellucida were collected per horn in WGA-treated group. Histologically, Con A caused vacuolization in epithelium and edema in the stromal layer of endometrium. However, such changes were not observed in WGA-treated uteri.