Loss of prostaglandin F2α, but not thromboxane, responsiveness in pregnant human myometrium during labour

Mar 29, 2008The Journal of endocrinology

Loss of response to prostaglandin in the pregnant uterus during labor, but not to thromboxane

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Abstract

Myometrium excised at late gestation displayed the greatest spontaneous activity compared with the tissues taken during labour (P<0.001).

Excitation from PGF2alpha was reduced after labour onset (P<0.01).
Responses to PGE2 at 10(-5) mol/l also decreased following the onset of labour.
U46619 consistently induced concentration-dependent contractions (P<0.001).
TP receptors play a crucial role in maintaining uterine muscle tone.
The findings suggest that TP receptors could be targeted for tocolytic therapies in pregnancy and labour-related issues.

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Prostaglandins (PG) E2, PGF2alpha and thromboxane (TX) mediate uterine contractility by targeting prostonoid EP, FP and TP receptors respectively. The aim of this study was to elucidate the function of these receptors in isolated human myometrium taken at term gestation prior to and following labour onset. Lower segment myometrial strips were immersed in organ baths in oxygenated Krebs' solution at 37 degrees C and connected to isometric force transducers. After equilibration, spontaneous activity and concentration responses to PGE2, PGF2alpha and U46619 (a stable TX mimetic) were measured as area under the curve and expressed as a percentage of the final contraction induced by hypotonic shock. Results were expressed as arithmetic means+/-s.e.m. and analysed using two-way ANOVA with Bonferroni's post hoc test. Myometrium excised at late gestation displayed the greatest spontaneous activity compared with the tissues taken during labour (P<0.001). Excitation evoked by PGF2alpha (P<0.01) and PGE2 at 10(-5) mol/l were attenuated after labour onset. U46619 consistently stimulated concentration-dependent contractions (P<0.001) and selective antagonists confirmed TP-mediated effects. The maintained responses to TX indicate crucial roles for TP receptors in the muscular tonus of the parturient uterus. This receptor and its secondary messenger system represent effective myometrial targets for tocolytic agents in both pregnancy and labour-associated disorders.

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Loss of prostaglandin F2α, but not thromboxane, responsiveness in pregnant human myometrium during labour

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