[Role of histamine as an intermediary in the action of estradiol on the rat uterus: inhibition of the hormonal induction of enzymes using histamine antagonists].

The administration of methiamide, a blocker of histamine H2-receptors, to rats was shown to prevent the induction of hexokinase (HK) and glucose-6-phosphate dehydrogenase (G-6PD) caused by both histamine and estradiol. An inhibitory effect of methiamide remained stable up to 16 h after histamine and estradiol administration. Diphenhydramine, a blocker of histamine H1-receptors, produces a short-term inhibitory effect on the HK and G-6PD activity stimulated by histamine and estradiol. The short-term nature of the diphenhydramine effect may be attributed to a low affinity to histamine H2-receptors and histamine fast dissociation. It may be concluded that some of the estradiol effects, particularly the HK and G-6PD induction in the uterus are histamine-mediated, apparently by means of H2-receptors. The administration of histamine to rats increases the uterus mass causing its inundation, and H1- and H2-blockers prevent this effect of histamine. However, the above histamine antagonists do not inhibit uterus inundation caused by estradiol. A conclusion is made that estradiol stimulates the uterus inundation not only by means of histamine but also by some other means.