A measurable reduction of s.r. Ca content follows spontaneous Ca release in rat ventricular myocytes.
The Ca content of the sarcoplasmic reticulum (s.r.) was measured in voltage-clamped rat ventricular myocytes from the integral of the Na-Ca exchange current evoked by applying caffeine to release the s. r. Ca content. Following spontaneous release of Ca from the s.r., the s.r. Ca content was decreased. The magnitude of this decrease was equal to that of the amount of calcium directly measured to have been pumped out of the cell during the spontaneous release. Following a spontaneous release, the s.r. Ca content recovered linearly. These results are shown to be consistent with the hypothesis that the frequency of spontaneous release is determined by the time taken for the cell and s.r. to reaccumulate the Ca2+ ions pumped out of the cell during spontaneous release.
Díaz
M E
ME
Department of Veterinary Preclinical Sciences, University of Liverpool, Liverpool L69 3BX, UK.
Trafford
A W
AW
O'Neill
S C
SC
Eisner
D A
DA
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002469:Cell Separation; D006352:Heart Ventricles; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger / Q000502:physiology; D013997:Time Factors
D019831:Sodium-Calcium Exchanger; D002110:Caffeine; D002118:Calcium