[Influence of endotoxin on sensitivity to oxytocin in pregnant rat myometrium].

Apr 1, 1995Nihon Sanka Fujinka Gakkai zasshi

How bacterial toxin affects the pregnant uterus's response to oxytocin in rats

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Abstract

Endotoxin increased myometrial sensitivity to oxytocin in the pregnant rat at preterm, with a pD2 value equal to that of term pregnant rats.

The hypersensitivity to oxytocin was significantly inhibited by indomethacin.
In myometrial strips exposed to endotoxin, concentrations of prostaglandins PGF2 alpha and PGE2 tended to increase during spontaneous contractions compared to controls.
Oxytocin administration led to a significant additional increase in PGF2 alpha production, which was also inhibited by indomethacin.
A dose-dependent stimulation of total inositol phosphate production by oxytocin was observed in the myometrium from preterm pregnant rats.
Inositol 1.4.5-trisphosphate production was significantly increased by oxytocin compared to controls.

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In order to clarify the mechanism of preterm labor induced by intrauterine infection, we studied the effect of endotoxin on oxytocin sensitivity of the myometrium in the pregnant rat. We administrated bacterial endotoxin obtained from Escherichia coli to the pregnant rat at preterm. By using a myometrial strip, we determined the effect of oxytocin on contractility, production of prostaglandins (PGs) and phosphoinositide hydrolysis. 1. Endotoxin increased myometrial sensitivity to oxytocin in the pregnant rat at preterm. The pD2 value was equal to that of myometrium taken from term pregnant rat. This hypersensitivity was significantly inhibited by indomethacin. 2. In the myometrial strips from rats to which endotoxin was administered, the concentrations of PGF2 alpha and PGE2 had already developed a tendency to increase during spontaneous contractions, when compared to the controls. There was seen a significant additional increase due to oxytocin. PGF2 alpha production was also significantly inhibited by indomethacin. 3. Oxytocin significantly stimulated total inositol phosphate production in a dose-dependent manner in myometrium taken from preterm pregnant rat. The inositol 1.4.5-trisphosphate production stimulated by oxytocin significantly increased in comparison to the controls. These results suggest that not only the production of PGs but phosphoinositide hydrolysis of transmembrane signaling pathways would play an important role in the mechanism of myometrial contraction at preterm when intrauterine bacterial infection developed.

[Influence of endotoxin on sensitivity to oxytocin in pregnant rat myometrium].

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