[Histamine receptors in the female reproductive system. Part II. The role of histamine in the placenta, histamine receptors and the uterus contractility].

The presence of the mast cells was confirmed not only in the uterus but also in the placental tissue. Mediators released from the placental mast cells may play a role in regulation of placental blood flow and normal blood pressure. Processes such uptake and clearance of vasoactive mediators may be upset in those women who developed pre-eclampsia. Histamine released from the placental mast cells may be involved in the mechanisms controlling myometrium contractility during the labour at term and preterm delivery. There is a correlation between the level of placental histamine and presence (or not) uterus contractility. Histamine produce a contractile response in isolated myometrial strips, in the majority of mammals, via H1 histamine receptors activation, but in some species e.g. rat, predominant response of uterus is relaxation (via H2 histamine receptors activation). Predominant response of the human uterus to histamine is contraction. Relaxation of human myometrial strips may be evoked after earlier usage of H1 receptors antagonists, although some H2 receptors agonists (e.g. dimaprit) induce the relaxation of human uterus without H1 receptors antagonists. Myometrium contractile activity is under control of sexual hormones. Neither the presence of H3 histamine receptors on the human myometrial smooth cells nor its role in the female reproductive system regulation was proved. Lack of the functional H3 receptors either on the smooth muscle cells or neuronal components of the animals' myometrium was shown in some studies.