The lack of effect of histamine on spontaneous activity in the isolated human myometrium

Effect of histamine on phasic and tonic contractions of isolated uterine tissue from pregnant women

OBJECTIVE

To enhance our understanding of the uterotonic effect of histamine, we compared the effects of histamine on spontaneous phasic and tonic contractile activity of uterine strips from term pregnant nonlaboring women.

STUDY DESIGN

Longitudinal uterine strips were used from the lower uterine segment of term pregnant nonlaboring women undergoing elective cesarean section. The concentration-response relationship to histamine (10(-8) to 10(-4) mol/L) was determined in spontaneously contracting strips or in strips contracted tonically with a protein kinase C activator (-)-indolactam V in the presence of H(1) receptor antagonist (S[+]-chlorpheniramine maleate), H(2) receptor antagonist (cimetidine), or solvent.

RESULTS

Histamine increased spontaneous phasic myometrial contractions in a concentration-dependent manner. H(1), but not H(2), receptor antagonist significantly attenuated the response to histamine. Histamine significantly reduced tonic contractions of uterine strips induced by indolactam V. H(1) histamine receptor antagonist abolished relaxation, whereas H(2) histamine receptor antagonist had no effect.

CONCLUSION

Histamine increases spontaneous, but inhibits tonic, contractions of uterine strips from term pregnant nonlaboring women. Both effects are mediated through activation of H(1) receptors.

Effect of histamine and histamine analogues on human isolated myometrial strips

1. The effect of histamine and histamine H1- and H2-receptor agonists on isolated myometrium strips of premenopausal women has been examined. The effect of acetylcholine was also determined. 2. Histamine, 2-pyridylethylamine, 4-methylhistamine and acetylcholine, but not dimaprit, produced a concentration-related contractile response in human isolated myometrial strips. Histamine also produced a further contraction in human isolated myometrial strips precontracted with KCl (55 mM). 3. The contractile response to histamine was antagonized by the histamine H1-receptor antagonist, clemizole (0.1 microM) but was potentiated by the histamine H2-receptor antagonist, ranitidine (10 microM). Clemizole (0.1 nM to 10 nM) competitively antagonized the contractile effect of 2-pyridylethylamine (- log KB = 10.5 +/- 0.5). The concentration-response curve for acetylcholine was displaced to the right by atropine 0.1 microM. 4. Atropine (0.1 microM), propranolol (0.1 microM), prazosin (0.1 microM) and indomethacin (1 microM) failed to modify the contractile response to histamine. 5. In human isolated myometrial strips precontracted with KCl (55 mM), clemizole at 1 microM completely abolished the contractile response to histamine and revealed a concentration-dependent relaxation. Dimaprit alone and 4-methylhistamine (in the presence of clemizole), produced concentration-related relaxation with a magnitude similar to that in response to histamine. The relaxant response to dimaprit was antagonized by ranitidine. 6. It is concluded that human isolated uterine strips possess histamine H1- and H2-receptors: the former mediating contraction and the latter relaxation. The predominant response to histamine in this tissue is contraction.

The mast cell and histamine concentration of the human post-menopausal uterus

Mast cells and histamine concentrations have been studied in uteri removed by hysterectomy from women in their post-menopausal years. Mast cell numbers were expressed as mean numbers/mm2 following fixation in 10% formalin and staining with Azure B. The majority of mast cells, in both the endometrium and myometrium, were very densely stained. Mast cells in the myometrium showed a significant negative correlation with years post-menopausal (rs = -0.52, P less than 0.05). Extracted histamine from uterine tissue was condensed with o-phthaldialdehyde to form a fluorophore and its fluorescence was measured at 450 microns using a spectrofluorometer. No significant correlation was found between histamine concentrations in the uterine wall and years post-menopausal.

Studies of the spontaneous motility and the effect of histamine on isolated myometrial strips of the nonpregnant human uterus: the influence of various uterine abnormalities

We investigated the spontaneous uterine activity of isolated corpus uteri myometrial strips from 30 patients with nonpathologic myometrium, 26 patients with uterine myoma, 23 patients with uterine adenomyosis, and three patients with uterine malignancy. We also investigated the influence of these conditions on the response of the uterus to histamine. The results show the same qualitative cyclic changes of the spontaneous motility of isolated myometrial strips throughout the menstrual cycle in all the abnormalities studied. These changes are characterized by a low amplitude and high frequency of spontaneous contractions in the proliferative phase and lower frequency with higher amplitude of contractions in the secretory phase. The isolated strips from patients with myomas present the highest spontaneous activity in reproductive age and preclimacteric women, but not in menopausal women. Histamine produced concentration-related contractions that are not significantly different in all the myometrial strips studied.