Summary. Intra-uterine contraceptive devices (IUDs) were made from monofilament nylon and inserted by a non-surgical technique through the cervical os of rats so as to be wholly within the uterine lumen. Most of these devices were retained and exhibited local contraceptive action in the uterine horn in which they were placed. This new method of insertion in rats offers advantages over other ways of studying the physiological and biochemical factors important to IUD function.Increasing acceptance of the intra-uterine contraceptive device (IUD) as a method of population control makes necessary a better understanding of the mechanism(s) of action of such devices. More familiarity with the precise contraceptive nature of IUDs will probably lead to increased use and improved effectiveness of these methods.The small size and low cost of the albino rat affords an opportunity for extensive laboratory investigations on the mechanism of IUD action. Further, the bicornate uterus of rats has proved to be especially advantageous since it offers the possibility of using the horn contralateral to the one containing the IUD as a control. Thus, although the control horn is independent and implanta¬ tion and pregnancy can occur normally, it is under the same general hormonal, genetic, nutritional and metabolic influences as the IUD horn in which blasto¬ cysts do not implant. Differences of any kind that can be demonstrated to exist between the horns are possible causes of the infertility induced by IUDs.A review of the literature on IUDs in rats and mice did not indicate that any investigators had inserted the devices through the cervix. All have been put in after laparotomy by sewing through the uterus, usually in two places (Doyle & Margolis, 1963, 1966Kar, Kamboj & Datta, 1964;Kar, Goswami, Kamboj & Chowdhury, 1964;Marston & Chang, 1964;Schuchner & Davidson, 1964;Chaudhury & Tarak, 1965;Greenwald, 1965;Parr, 1966;Speilberger & Olewine, 1966;Havránek, Dyková & Tichy, 1967;Laumas & Farooq, 1967).Since insertion through the cervix seemed to offer advantages over the trau¬ matic method being used, and further, since the cervical approach was more closely analogous to the practice in man, we investigated the efficacy of produc¬ ing unilateral sterility by insertion of a device wholly within the uterine lumen. G 515
The sequence of water and electrolyte events was followed during development of deciduoma in rats. Minutes after scratching the endometrium, Na and Cl increased and K decreased, probably due to the influx of blood. These changes were followed by a water imbibition at 24 and 48 hours and an increase in K. Damaged horns increased in weight and width during this period. Water and electrolyte alterations were similar in ovariectomized rats. ovariectomized rats given progesterone, and intact rats during the first 48 hours, suggesting that these initial effects were due to the inflammation resulting from the injury inflicted. During the next 48 hours injured uterine horns of ovariectomized rats regressed and composition approached that of uninjured tissue. In contrast, composition of injured horns of progesterone rats or rats with intact ovaries was markedly different from uninjured tissue. Decidual tissue H2O, K, Na and Cl were significantly higher than in undeveloped uterine horns. Ionic composition characteristic of decidual growth was remarkably similar to the ionic pattern exhibited during the inflammatory state.
This experiment was planned to determine conditions favourable to the development of leucocytic invasion and exudate formation in uterine horns bearing intrauterine devices (IUDs). Three groups of rats were examined: (A) pregnant in one uterine horn and bearing an IUD in the contralateral horn, (B) pseudopregnant after mating to vasectomized males and bearing unilateral IUDs, and (C) pseudopregnant following mating to intact males and bearing bilateral
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