Expression of the calcium-activated potassium channel in upper and lower segment human myometrium during pregnancy and parturition

Myometrial biopsies were collected from non-pregnant women at hysterectomy and pregnant women at either elective caesarean section or emergency caesarean section. Protein expression level and cellular localization of BKCa alpha- and beta-subunit in US and LS myometrium were determined by Western blot analysis and immunohistochemistry, respectively.BKCa alpha- and beta-subunit were predominantly localized to myometrial smooth muscle in both US and LS myometrium obtained from non-pregnant and pregnant patients. The level of BKCa alpha-subunit in US but not in LS was significantly higher in NP myometrium than those measured in myometrium obtained during pregnancy. Lower expression of BKCa alpha-subunit in both US and LS was found in TL than in TNL biopsies. Expression of beta-subunit in both US and LS myometrium was significantly reduced in TL group compared with those measured in TNL group. There was no significant difference in BKCa beta-subunit expression in either US or LS between NP and TNL group.Our results suggest that expression of BKCa alpha- and beta-subunit in pregnant myometrium is reduced during labour, which is consistent with the myometrial activity at the onset of parturition.During most of pregnancy, myometrium activity is characterized by poorly coordinated contractures. In late pregnancy, the uterus undergoes preparedness for the stimuli that lead to contractility and labour [1,2]. The mechanisms that initiate labour in women, particularly the molecular processes that convert the myometrium form a state of relative quiescence to the activated and contractile state, are not well understood. An understanding of these processes, at the molecular and cellular level, is essential to developing novel therapeutic strategies for management of associated clinical problems such as preterm labour that accounts for 85% of all perinatal complications and death.It has been known that uterine myometrial contractility at term is triggered by a number of physiologica