Degranulation of uterine mast cell modifies contractility of isolated myometrium from pregnant women

Objective This study was undertaken to test that uterine mast cell degranulation alters human myometrial contractility in vitro and to define what mediators are involved in this process. Study design Longitudinal myometrial strips prepared from biopsy specimen obtained from the lower uterine segment of women at preterm and term gestation (with and without labor) were studied. Contractile responses to compound 48/80, a mast cell degranulator, were compared in the absence or presence of a mast cell stabilizer, H1 and H2 receptor antagonists, cyclooxygenase, and lipoxygenase inhibitors. Results Compound 48/80 increased myometrial contractility in all groups. The mast cell stabilizer cromolyn inhibited contractility, whereas the cyclooxygenase inhibitor ibuprofen, the H1-receptor antagonist S(+)-chlorpheniramine maleate, but not the H2 antagonist cimetidine, only slightly attenuated this effect. The lipoxygenase inhibitor linoleyl hydroxamic acid augmented the responses to compound 48/80 in the preterm but not in the term group. Conclusion Uterine mast cell degranulation, or the effects of their mediators, can modulate uterine contractility during pregnancy