Expression And Significance Of Large Conductance Ca²⁺ Activated K⁺ Channel And Its Relationship With Caveolin In Myometrium In Postpartum Hemorrhage

ObjectiveThe purpose of this study was to detect the expression of large conductance Ca2+ activated K+ channel(BKCa) and its relationship with caveolin in myometrium of patients with postpartum hemorrhage(PPH), discuss their roles in the pathogenesis of PPH caused by uterine atony.MethodsThe levels of contractile frequency, amplitude and contraction of myometrium were detected by RM6240 biological experimental system; the BKCa(α,βsubunit) protein expression levels in myometrium were detected by Western blot; the BKCa(α,βsubunit) mRNA expression levels in myometrium were detected by real-time fluorescent quantitative reverse transcription-polymerase chain reaction for women with PPH caused by uterine atony(study group, n=30) and normal uterine smooth muscle contraction(control group, n=30), who presented to Fujian Matrenity and Child Health Hospital for low cervical caesarean section from October 2009 to February 2011.The co-immunolocalizations of BKCa(αsubunit) and caveolin-1, BKCa(αsubunit) and caveolin-2 in myometrium were exzamined by double-immonofluorescence labeling and confocal laser microscopy; the interactions of BKCa(αsubunit) and caveolin-1, BKCa(αsubunit) and caveolin-2 in myometrium were comfirmed by co-immunoprecitation for all subjects.Results①In study group, the levels of myometrium contractile frequency, amplitude and contraction were lower than that of their controls(P<0.05).②In study group, BKCa (α,βsubunit) protein and mRNA expression in myometrium were significantly higher than in control group(P<0.05).③Both groups, BKCa (α,βsubunit) protein and mRNA level in myometrium was negatively related to the level of myometrium contraction.④Both groups, BKCa(αsubunit), caveolin-1 and caveolin-2 were detected in myometrium; BKCa(αsubunit) localized primarily on the plasma membrane, whereas caveolin-1 and caveolin-2 localized to intracellular and pasma membrane compartments; BKCa(αsubunit) and caveolin-1, BKCa(αsubunit) and caveolin-2 co-immunolocalized on part of the myometrial smooth muscle cell membrane.⑤In study group, both BKCa(αsubunit)- caveolin-1 complex and BKCa(αsubunit)- caveolin-2 complex in myometrium were significantly higher than that of control group(P<0.05)..⑥Both groups, BKCa(αsubunit)- caveolin-1 complex level and BKCa(αsubunit)- caveolin-2 complex level in myometrium was negatively related to the level of myometrium contraction.Conclusions①The uterine smooth muscle is a kind of single-unit smooth muscle with property of autorhythmicity, which make it possible the automatic contraction be detected in vitro. The application of muscle isometric tension experiment in the study of myometrium contraction is feasible.②Increased BKCa (α,βsubunit) expression in myometrium may be strongly correlated with the reduction of myometrium tension.③Increased BKCa (α,βsubunit) expression in myometrium may be involved in the pathogenesis of PPH caused by uterine atony.④There exists BKCa(αsubunit), caveolin-1 and caveolin-2 in uterine smooth muscle cells, BKCa(αsubunit) and caveolin-1, BKCa(αsubunit) and caveolin-2 co-locates on part of the myometrial smooth muscle cell, suggesting caveolins involve in regulating the expression of BKCa.⑤Increased expression of BKCa(αsubunit)- caveolin-1 complex and BKCa(αsubunit)- caveolin-2 comlex in myometrium may be strongly correlated with the reduction of myometrium tension. ⑥Caveolins may participate in the pathogenesis of PPH caused by uterine atony via regulating the expression of BKCa by its interaction with BKCa(αsubunit).