Quantitative immunoconfocal analysis of human myometrial gap junction connexin43 in relation to steroid hormone concentrations at term labour.

The aim of this study was to quantify gap junction expression in the human myometrium in relation to progesterone and oestradiol concentrations, and to establish whether oxytocin-resistant dystocia is due to an abnormality in gap junction expression. Three groups of patients were investigated: (i) before labour (at term), (ii) normal labour and (iii) oxytocin-resistant dystocia (eight patients per group). For each patient, the concentrations of oestradiol and progesterone in maternal blood and in myometrial tissue were measured, and the number and area of immunostained connexin43 gap junctions per unit volume of tissue determined by quantitative analysis of digital images obtained by confocal microscopy. No significant difference in connexin43 gap junction content was observed between the three patient groups. When all groups were pooled, there was a significant positive correlation (P < 0.05) between the quantity of immunolabelled gap junctions and the oestradiol:progesterone ratio, but there was no significant difference in this correlation between the groups. Gap junction immunolabelling was not correlated with the progesterone or oestradiol concentration in the maternal blood or the myometrium. These data suggest that in human myometrium: (i) dystocia is not due to a reduced level of immunodetectable connexin43 gap junctions, (ii) onset of labour is not associated with a sudden increase in immunodetectable gap junction protein and (iii) gap junctions can be expressed in the presence of high progesterone concentrations.