Activation of Ca2+-activated Cl- current by depolarizing steps in rabbit urethral interstitial cells

Smooth Muscle Group, Department of Physiology, The Queen's University of Belfast, Belfast BT9 7BL, Northern Ireland, United Kingdom Submitted 6 September 2002 ; accepted in final form 25 March 2003 Interstitial cells were isolated from strips of rabbit urethra for study using the amphotericin B perforated-patch technique. Depolarizing steps to -30 mV or greater activated a Ca 2 + current ( I Ca ), followed by a Ca 2 + -activated Cl - current, and, on stepping back to -80 mV, large Cl - tail currents were observed. Both currents were abolished when the cells were superfused with Ca 2 + -free bath solution, suggesting that Ca 2 + influx was necessary for activation of the Cl - current. The Cl - current was also abolished when Ba 2 + was substituted for Ca 2 + in the bath or the cell was dialyzed with EGTA (2 mM). The Cl - current was also reduced by cyclopiazonic acid, ryanodine, 2-aminoethoxydiphenyl borate (2-APB), and xestospongin C, suggesting that Ca 2 + -induced Ca 2 + release (CICR) involving both ryanodine and inositol 1,4,5-trisphosphate receptors contributes to its activation. interstitial cells; urethra; calcium-activated chloride current; calcium-induced calcium release; inositol 1,4,5-trisphosphate; ryanodine Address for reprint requests and other correspondence: K. D. Thornbury. Smooth Muscle Group, Dept. of Physiology, The Queen's Univ. of Belfast, 97 Lisburn Rd., Belfast BT9 7BL, Northern Ireland, UK (E-mail: k.thornbury{at}qub.ac.uk ).