TEMPORAL-DEPENDENT AND HORMONE-DEPENDENT CHANGES IN UTERINE SENSITIZATION FOR THE DECIDUAL CELL REACTION AND DECIDUALIZATION IN-VITRO OF RAT ENDOMETRIAL STROMAL CELLS

The ability of endometrial stromal cells from nonsensitized rat uteri to undergo decidualization in vitro was investigated. Cells were obtai ned by enzymatic dispersion from uteri of ovariectomized, steroid-trea ted rats at the equivalent of day 4, 5 or 6 of pseudopregnancy, or on day 5 from rats treated with 0, 0.3 or 1.0 mu g oestradiol (low, inter mediate or high doses of oestradiol, respectively) on day 4, and cultu red for 24, 48 or 72 h. Decidualization in vivo, as assessed by uterin e mass 5 days after the unilateral intrauterine injection of 100 mu l sesame oil, was maximal for rats receiving the deciduogenic stimulus o n day 5 and treated with the intermediate dose of oestradiol. Under co ntrol conditions in vitro, alkaline phosphatase (ALP) activity, the in crease in ALP activity with time, and prostaglandin E(2) (PGE(2)) accu mulation in the medium were greatest for cells from maximally sensitiz ed uteri. Indomethacin, an inhibitor of PG synthesis, reduced PGE(2) a ccumulation to barely detectable amounts, and decreased ALP activity, especially in cells from maximally sensitized uteri, indicating that e ndogenous PG production contributed to the increase in ALP activity in these cells. The addition of PGE(2), with indomethacin increased ALP activities. However, ALP activities were lower for cells derived from nonsensitized uteri when compared with cells from maximally sensitized uteri. These results suggest that endometrial stromal cells from nons ensitized uteri have a reduced capacity to undergo decidualization in vitro, and that this reduced capacity is not explained by differences in PGE(2) production.