CONTRACTILE AGONISTS PREFERENTIALLY ACTIVATE CL(-) OVER K+ CURRENTS IN ARTERIAL MYOCYTES

Simultaneous patch-clamp and Ca2+ fluorescence measurements have revea led depolarising oscillations in the membrane potential of arterial (p ulmonary) myocytes in response to adenosine 5'-triphosphate (ATP) and endothelin-1 (ET-1). These oscillations (i) are due to the preferentia l activation of Ca2+-activated Cl-, over K+ currents, (ii) occur throu gh a mechanism involving Ca2+ release from intracellular Ca2+ stoles a nd (iii) are Likely to promote constriction, These results provide a n ovel perspective into the relative contribution and importance of Ca(2 +)activated Cl- and K+ channels in controlling membrane potential of a rterial smooth muscle in response to contractile agonists. (C) 1996 Ac ademic Press, Inc.