Sensitivity of ovine myometrial tissue to various eicosanoids in vitro

The sensitivity of sheep myometrial tissue to prostaglandin F2 alpha (PGE2 alpha), PGE2, the thromboxane analog U-44069, and leukotrienes C4 (LTC4) and LTD4 was investigated in a superfusion system. Tissues were obtained from eight oophorectomized ewes, with or without pretreatment with estradiol-17 beta. After equilibration, spontaneous activity was abolished by adding indomethacin to the superfusion fluid. The dose needed to induce a contraction with a peak level of 50% of the median peak level of spontaneous contractions increased from PGE2 to PGF2 alpha, U-44069, LTC4, and LTD4. The differences between the doses required were significant for all compounds, except between LTC4 and LTD4. Estradiol-17 beta pretreatment caused an increase in the required dose of PGF2 alpha. The results of this study do not support the hypothesis that leukotrienes are involved in the regulation of myometrial activity.