Varying effects of an IUD on decidualization in mice

Abstract

Chronically implanted IUDs consisting of silk suture threads induced decidualization in regions of the uterus remote from the suture site in ovariectomized mice treated with a regimen of progesterone and oestrogen which sensitizes the uterus to a decidual stimulus. In these conditions the IUDs did not inhibit decidualization induced by instilled oil, although they did so in pregnant animals of the same strain. Varying the dose of progesterone and oestrogen did not produce conditions in which IUD's inhibited oil-induced decidualization in ovariectomized mice and progesterone treatment did not prevent IUDs inhibiting decidualization in pregnant animals. However, when ovariectomized mice, sensitized as before, were primed repeatedly with oestrogen to simulate continuing oestrous cycles after IUD insertion, the IUD's inhibited oil-induced decidualization. This involved the premature loss of instilled oil from the uterine lumen and was associated with heavy infiltration of leucocytes into the luminal epithelium. Numbers of leucocytes free in the uterine lumen did not appear to be critical. It appears that contact between the oil and the luminal epithelial surface must be sustained for some length of time to induce a decidual reaction; brief contact is not sufficient to trigger the response.

The sensitivity of the uterus of the mouse and rat to intraluminal instillation

“…4). Although Martin & Finn (1979) observed that the oil had disappeared from most IUD-bearing uteri 44 h after injection, in the present study it was still evident at 6 h. The complete failure of this oil to induce a vascular reaction suggests that the IUD-bearing uterus shows a general insensitivity to potential deciduogenic stimuli. This would also be consistent with the fact that there was little increase in uterine vascular permeability even in the region of the IUD thread itself.…”

“…The degree of continuity between the lumina of the two uterine horns of mice seems to undergo subtle changes: in contrast to the findings in ovariectomized females, instilled materials rarely cross to the contralateral horn after oestradiol and progesterone treatment (Martin & Finn, 1979; unpublished observation). The relative independence of the two horns after progesterone plus oestradiol treatment is reflected by the generally isolated response of the instilled horn.…”

“…4). Martin & Finn (1979) suggested that the failure of oil to induce decidualization in the presence of an IUD might be due to changes in myometrial activity and the premature loss of the oil stimulus from the uterus. This explanation would not account, however, for the failure of oil to induce the increase in vascular permeability that normally follows immediately after oil instillation (Exp.…”

“…At the time of ovariectomy, a silk thread (to serve as an IUD) was inserted into the top half of each uterine horn of some of the mice in this experiment. At 2 weeks after ovariectomy, all mice were primed with 100 ng oestradiol-17ß for 3 consecutive days per week for the next 3 weeks: this schedule allows the full development of the potential IUD effect (Martin & Finn, 1979). At the beginning of the 4th week the females received 3 daily injections of progesterone (1 mg) and oestradiol ( 10 ng).…”

On the source of uterine 'luminal fluid' proteins in the mouse

“…Randomly bred female Swiss Schneider mice were housed, allowed to become pregnant, or ovariectomized as described by Martin & Finn (1979 10:30-11:30 h on Day 5. At 15 min before death they were anaesthetized with tribromoethanol and given 0-2 ml of 2% Pontamine Blue i.v.…”