Uterine vascular permeability after uterine stimulation to rats differentially sensitized for the decidual cell reaction.

Uterine vascular permeability (VP) was assessed after unilateral intrauterine injection of sesame oil to rats given either optimal sensitization for the decidual cell reaction or one of several forms of suboptimal sensitization. The study was intended to determine the relationship between changes in uterine VP and imminent endometrial decidualization. Uterine VP was estimated by the rate at which the uterine volume of distribution of i.v. injected 125I-labeled albumin approached the uterine extracellular fluid volume (ECFV). When ideal sensitization was provided, uterine VP was significantly greater in stimulated than nonstimulated horns at 4, 8, 16, and 32 h after stimulation (p < 0.05). Maximum VP in stimulated horns occurred at 8 h, with the time for the 125I-labeled albumin volume to reach half the uterine ECFV (t1/2) estimated to be 30 min. Different types of sensitization resulted in different levels of uterine VP in stimulated and nonstimulated horns, with maximal VP occurring in stimulated horns of rats that had previously received optimal sensitization for decidualization. We conclude that endometrial decidualization is preceded by significant increases in uterine VP and that optimal sensitization promotes an optimal VP response.