LEUCOCYTIC AND INFLAMMATORY EXUDATE IN THE UTERI OF PREGNANT AND PSEUDOPREGNANT RATS BEARING IUDS

The article describes an investigation to determine conditions favorable to development of leucocytic invasion and exudate formation in uterine horns bearing IUDs. Nylon double S-shaped IUDs were used on 125 adult Wistar rats. Rats were divided into 3 groups: 1)pregnant in 1 utertine horn and bearing an IUD in the contralateral horn 2)pseudopregnant after mating to vasectomized males and bearing unilateral IUDs 3) pseudopregnant following mating to intact males and bearing unilateral IUDs. Volume of packed-cells obtained from horns containing IUDs contralateral to 15 day pregnant horns was significantly greater (p less than .001) than from IUD horns contralateral to pseudopregnant horns. Packed-cell volumes form IUD horns of the pregnant group also was much greater (p less than .001) than those of pseudopregnant horns where both horns had an IUD. About 75 percent of Group 1 IUD horns contained visible leucocytic exudate. IUD horns of Group 2 were sparsely populated with cells 34 percent were found with leucocytes. Rats of Group 3 showed no evidence of leucocytic infiltration in 71 percent of the horns and the remaining 29 percent showed very small numbers of cells. Differences in packed-cell volumes of luminal material flushed from uterine horns with IUDs indicates that pregnancy in the opposite horn sustains the higher cellular content. Differences may indicate that the pregnant rat is more susceptible to infection and/or infammatory reactiony The recovery of IUDs from rats fitted with the unilateral device and who subsequently became pregnant indicates an 85 percent retention of the IUD. Effectiveness of IUD as a contraceptive in horns retaining it was 97 percent. Only 1 rat had embryos in a horn containing an IUD.