Endogenous mast cell degranulation modulates cervical contractility in the guinea pig

OBJECTIVE: The purpose of this study was to investigate the effect of endogenous mast cell degranulation on the contractility of isolated cervical strips from nonpregnant and pregnant guinea pigs. STUDY DESIGN: Longitudinal cervical strips from nonpregnant and pregnant (mid and term) guinea pigs were used for isometric tension recording. Responses to the mast cell degranulating agent, compound 48/80, were compared in the absence or presence of different inhibitors and receptor antagonists. Concentration-response curves were obtained to histamine and 5-hydroxytryptamine in strips that were incubated with antagonists or solvent. RESULTS: Compound 48/80 and histamine significantly increased contractility of cervical strips in all 3 groups of animals. The inhibitor of mast cell degranulation significantly reduced responses to compound 48/80 and histamine-1 receptor antagonist reduced responses to histamine in all 3 groups. Histamine-1 receptor antagonist significantly inhibited responses to compound 48/80 in nonpregnant and mid pregnant guinea pigs. Histamine-2 receptor antagonist did not alter responses to compound 48/80 nor to histamine. The receptor antagonist 5-hydroxytryptamine-2 significantly inhibited cervical contractility that was induced by compound 48/80 in tissues from mid pregnant and term pregnant guinea pigs. Lipoxygenase inhibitor was effective in mid pregnant guinea pigs. Cyclooxygenase inhibitor, 5-hydroxytryptamine, and a combination of lipoxygenase and cyclooxygenase inhibitors had no effect on cervical contractility. CONCLUSION: The degranulation of mast cells releases histamine and other mediators that stimulate cervical contractility through histamine-1 receptors. Cervical infiltration and modulation of contractility by mast cells may play an important physiologic and/or pathologic role in the control of cervical function during pregnancy. (Am J Obstet Gynecol 2002;186:438-45.)