RELATIONSHIP BETWEEN ANDROSTENEDIONE-INDUCED MYOMETRIAL CONTRACTIONS AND PLATELET-ACTIVATING-FACTOR ACETYLHYDROLASE IN LATE-GESTATION IN PREGNANT RHESUS-MONKEYS

An association between platelet-activating factor (PAF) and myometrial contractions has been established. Estrogens regulate PAF activity vi a reduction in the activity of plasma PAF acetylhydrolase (PAF-AH), th e enzyme that catalyzes PAF inactivation. Administration of androstene dione to pregnant monkeys leads to sustained increases in maternal pla sma estradiol (E(2)), with persistent nocturnal myometrial contraction s. The present study tested the hypothesis that androstenedione-induce d contractions are associated with a fall in maternal plasma PAF-AH ac tivity in monkeys. Eight monkeys (132-136 days gestation, dGA) were in strumented under halothane anesthesia with maternal vascular catheters and uterine electromyogram electrodes. At 138-142 dGA, two baseline m aternal arterial samples were taken for E(2) and PAF-AH measurements. The following day a continuous i.v. androstenedione infusion was start ed in 4 monkeys while 4 control monkeys received i.v. infusions of veh icle alone. Arterial brood sampling was repeated 1 and 3 days after th e start of either infusion. Despite an increase in maternal E(2) to te rm levels and established myometrial contractions, no change in matern al plasma PAF-AH activity occurred after androstenedione treatment. Ma ternal plasma E(2), PAF-AH activity, and contractions remained unchang ed from baseline in control monkeys. In conclusion, androstenedione-in duced increases in maternal plasma E(2) and myometrial contractions ar e not associated with a fall in maternal plasma PAF-AH specific activi ty.