ACTIVITY OF GLIBENCLAMIDE-SENSITIVE K-MUSCLE CELLS OF PIG PROXIMAL URETHRA( CHANNELS UNDER UNSTIMULATED CONDITIONS IN SMOOTH)

The membrane potential in pig proximal urethra was examined by use of the microelectrode technique. In cells 1-2 cm from the bladder neck th e membrane potential was quiescent, with a value of -37.2+/-2.5 mV (n = 16). In some cells small spontaneous de-and hyperpolarizations were seen. Glibenclamide (1 mu M) caused a small but significant depolariza tion in tissue strips (12+/-3 mV, n = 3) and also in dispersed cells u sing whole-cell patch electrodes (13+/-3 mV, n = 5). In the convention al whole-cell voltage-clamp configuration, glibenclamide reduced the n oise level of the basal membrane current at -50 mV and inhibited the m embrane current in symmetrical 140 mM K+ conditions. In cell-attached patches, brief openings of a glibenclamide-sensitive 43 pS K+ channel (K-GS-43 pS) were seen even under unstimulated conditions and greater activation occurred in the same membrane patch on subsequent applicati on of 100 mu M levcromakalim. These results provide direct evidence th at glibenclamide-sensitive K+ channels may play a role in maintaining the resting membrane potential of pig proximal urethra under unstimula ted conditions.