Effect of Direct Injection of Neutrophils from Uterine Horns of Rats Containing Intrauterine Devices into Recipient Pregnant Uteri

Abstract

The purpose of this study was to determine whether or not neutrophils from uterine horns containing an intruterine device (IUD) inhibit implantation of rat blastocysts. On day 4 (6:00 P.M. to 8:00 P.M.) of gestation the uterine horns of the recipient rats were exposed and injected with neutrophils, supernatant luminal fluid, or Hanks' solution. The total volume injected was 30 mul. All of the rats were killed on day 12 of pregnancy, and the number of fetuses and resorption sites was determined. The data show that, in rats injected with neutrophils on day 4 of gestation, implantation was significantly increased as compared with controls injected with Hanks' (vehicle) solution. Whether the supernatant fluid had an effect in suppression of implantation could not be determined, since the effect was not statistically different from that observed in either the vehicle- or neutrophil-injected groups. However, the responses observed with the supernatant-injected groups. However, the responses observed with the supernatant-injected group were intermediate between those of the control horns and those of the neutrophil-injected horns. The finding supports the concept that in IUD-bearing animals in which there is a rapid influx of neutrophils the cells play a major role in suppressing implantation.