CALCIUM-DEPENDENT K-CHANNELS IN GUINEA-PIG AND HUMAN URINARY-BLADDER

This study provides evidence for the presence of large conductance Ca2 +-dependent K-channels in guinea pig and human urinary bladder smooth muscle. A23187, a Ca2+-ionophore, increased charybdotoxin and iberiato xin sensitive K-42 efflux in human urinary bladder smooth muscle cells , suggesting that large conductance Ca2+-dependent K-channels are pres ent in these cells. NS004, a large conductance Ca2+-dependent K-channe l opener, relaxed guinea pig bladder strips precontracted with 15 mM K Cl which is inhibited by iberiatoxin. In addition, NS004 also evoked a n iberiatoxin sensitive increase in Rb-86/K-42 efflux in guinea pig an d human urinary bladder smooth muscle cells, demonstrating that NS004 activates large conductance Ca2+-dependent K-channels to achieve its r elaxation effect in the bladder. (C) 1995 Academic Press, Inc.