STRETCH ACTIVATES NONSELECTIVE AND K-CELL CURRENTS IN GUINEA-PIG URINARY-BLADDER MYOCYTES( WHOLE)

The increase in intravesicular pressure upon rapid filling of the urin ary bladder is attributed to stretch-activated non-selective cation ch annels (SACs). Inward currents through SACs were measured not on the s ingle-channel level but also in the wholecell configuration. Whole-cel l stretch and activation of SACs can depolarize the membrane and induc e Ca2+ action potentials. Ca2+ influx through both SACs and voltage-ga ted Ca2+ channels increases the intracellular Ca2+ concentration and a ctivates contraction. Further, it activates BK+ channels thereby promo ting repolarization. Thus, lengthening of single bladder myocytes can induce repetitive de- and repolarizations as they are observed when th e bladder is filling in vivo.