Are leukotrienes involved in human uterine contractility?

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 microM; nor did they have any effect in rat non-pregnant myometrium. As expected, PGE2, PGF2 alpha (0.3 microM) and oxytocin (5 nM) stimulated human pregnant myometrium. PGF2 alpha 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 greater than LTD4 much greater than LTE4, LTB4, PGE2, PGF2 alpha, 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.