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Ca-activated chloride current and Na-Ca exchange have different timecourses during sarcoplasmic reticulum Ca release
A W Trafford1, M E Díaz, D A Eisner
1Department of Veterinary Preclinical Sciences, The University of Liverpool, Brownlow Hill and Crown Street, Liverpool, L69 3BX, UK.
Abstract:
The aim of this work was to measure membrane currents activated by Ca release from the cardiac sarcoplasmic reticulum (s.r.). Intracellular Ca concentration ([Ca2+]i) was measured using fluo-3 in patch clamped cells. Calcium release from the s.r. (whether occurring spontaneously or evoked by caffeine) produced changes of membrane current which could be separated into a Ca-activated Cl current which was inhibited by DIDS or Cl removal and a Na-Ca exchange current. Both these currents had different time courses from the measured [Ca2+]i. Furthermore the Ca-activated Cl current decayed more quickly than did Na-Ca exchange. Possible explanations for the different kinetics of these two Ca-sensitive currents are discussed.