The Leukocytic Response to an Intrauterine Foreign Body in the Rabbit

Abstract

39 New Zealand white female rabbits and 15 Sprague-Dawley female rat s were used to determine if a relatively small silicone plastic intrauterine foreign body (IUFB) would produce an incomplete antifertility action and to correlate the number of inflammatory cells in the uterine fluid with the presence or absence of pregnancy in the IUFB uterine horn. Rabbits were bred 5 days after devices were inserted and rats 3 days after. Both species were sacrificed 10 days postcoitus. Corpora lutea were counted uterine horns flushed implantations noted and cells enumerated. Of 39 rabbits 33 had corpora lutea in both ovaries and each had 1 or more implantation sites. 6 were classified was nonpregnant due to mating failure. There was a significant difference in fertility rates between the 33 control horns and the 33 IUFB horns (.86 vs. .5 p less than .001). There was also a significant difference in the mean number of leukocytes in the ut erine flushings of the IUFB side compared to the control side (32.6 vs. 3/cu. mm p less than .001). As the number of leukocytes increased in the IUFB horns the fertility rate diminished. The implantation site size was significantly smaller in the IUFB horn (p less than .001). Those animals with longer uterine horns containing IUFBs also had more implantation sites than those with shorter horns. The maximum infertility effect of the IUFB was exerted in the immediate vicinity of the device. Also sections of endometrium taken at a distance from the IUFB showed fewer polymorephonuclear leukocytes than in areas nearer to the IUFB. No evidence of resorption of embryos or placentas was found in any horns. In rats the IUFBs almost completely prevented pregnancy in those horns where placed; in the control horns pregnancies were of no rmal frequency (p less than .001). There was a significant difference i n the number of leukocytes in uterine flushings in IUFB and control rats (643 vs. 11 leukocytes/cu. mm p less than .001). When pregnancies occurred in the rabbit IUFB uterine horn the number and size of implantations were found to be inversely proportional to the total number of leukocytes present. The distance of implantation sites from the IUFB was directly proportional to the quantity of leukocytes.