Altered expression of calcium-activated K and Cl channels in detrusor overactivity of rats with partial bladder outflow obstruction

• To evaluate the activity of large- and small-conductance calcium-activated potassium channels (BKCa, SKCa) and calcium-activated chloride channels (ClCa) in detrusor overactivity (DO) cells after partial bladder outlet obstruction (PBOO) in rats. MATERIALS AND METHODS Thirteen female Wistar rats with DO caused by PBOO were studied simultaneously with eight sham-operated rats. The expression of KCa and ClCa channels was assessed by reverse transcription-polymerase chain reaction, and the function of the two groups compared. RESULTS In the DO cells the expression of BKCa, SKCa2 and SKCa3 was lower, and that of ClCa channels higher, than in the control group cells. Using confocal laser scanning microscopic analysis, the function of BKCa and SKCa channels was suppressed, and that of ClCa channels was enhanced in DO group cells. KCa and ClCa effectors altered the cell membrane potentials more significantly in the DO cells than in the control cells, indicating a decrease in KCa and an increase in ClCa in DO group in either iso- or hypo-osmolar medium. Moreover, the change in BKCa, SKCa and ClCa channel activators in DO cells showed a more excitable state in hypo-osmolar medium than in iso-osmolar medium. CONCLUSION In DO myocytes after PBOO, the expression and function of KCa channels were decreased, and those of ClCa channels increased. These changes all provoke greater cell excitability, and could partly account for the DO.

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