Are leukotrienes involved in human uterine contractility?

Summary. The effects of leukotrienes (LT) on the contractility of human and rat myometrial strips in vitro were compared with the effects of prostaglandins (PGs) and oxytocin. Preparations of human myometrial membranes were investigated for the presence and characteristics of LTC₄ receptors. Neither the peptido-leukotrienes (LTC₄, LTD₄, LTE₄) nor LTB₄ had any consistent effect, stimulatory or inhibitory, on human pregnant or non-pregnant myometrium, at doses up to 1·25 μM; nor did they have any effect in rat non-pregnant myometrium. As expected, PGE₂, PGF_2α (0·3 μM) and oxytocin (5 nM) stimulated human pregnant myometrium. PGF_2α stimulated and PGE₂ inhibited human non-pregnant myometrium but oxytocin had no effect; all three compounds stimulated rat non-pregnant myometrium. The binding of ³H-LTC₄ to human myometrium was specific (LTC₄> LTD₄ >>> LTE₄, LTB₄, PGE₂, PGF_2α, arachidonic acid) but of low affinity compared with the binding of ³H-PGE₂ to the same membrane preparations. These data support the view that leukotrienes have little direct influence on myometrial contractility.