5-Hydroxyeicosatetraenoic acid, leukotriene C4, and prostaglandin F2 alpha in amniotic fluid before and during term and preterm labor.

Arachidonic acid is metabolized by cyclooxygenase leading to prostaglandins and by lipoxygenases leading to hydroxyeicosatetraenoic acids (HETE) and leukotrienes (LT). Prostaglandins are potent uterine constrictors. 5-HETE and LTC4 also stimulate uterine contractions but their role in labor is not known. To estimate the activities of these pathways before parturition and their relationship to uterine contractility, amniotic fluid concentrations of 5-HETE, LTC4, and prostaglandin F2 alpha (PGF2 alpha) were determined in five chronically catheterized rhesus monkeys. Uterine contractility was continually assessed by recording changes in amniotic fluid pressure. The results obtained indicate the following conclusions: (1) 5-HETE and LTC4, but not PGF2 alpha, are associated with uterine contractility after preterm intrauterine surgery. Surprisingly, amniotic fluid PGF2 alpha, levels were nondetectable for 1 to 2 weeks after surgery. (2) 5-HETE and LTC4 are present in higher concentrations than PGF2 alpha in amniotic fluid. (3) 5-HETE, LTC4, and PGF2 alpha all increase with the onset of labor. Amniotic fluid concentrations of 5-HETE and LTC4 are significantly higher than those of PGF2 alpha before and during term and preterm labor. (4) Labor can occur with suppressed PGF2 alpha levels but with increasing 5-HETE and LTC4 levels. (5) These data suggest that 5-HETE and LTC4 are important components of the parturitional process.