One calcium ion may suffice to open the tetrameric cardiac ryanodine receptor in rat ventricular myocytes. Export

@article{citeulike:3023421, abstract = {1. The release of Ca2+ from sarcoplasmic reticulum in response to Ca2+ entering through L-type Ca2+ channels was studied in isolated voltage clamped rat ventricular myocytes at room temperature using the fluorescent Ca2+ indicators fluo-3 and Oregon Green 488 Bapta 5N. 2. Depolarizations to positive potentials elicited fluo-3 Ca2+ transients with rates of rise that were linearly related to the magnitude of the peak measured Ca2+ current in the presence of Cs+-containing pipette solutions. 3. Further experiments utilizing prepulses to preactivate a constant number of channels also revealed a linear relationship between the Ca2+ transient rate of rise and the magnitude of entering Ca2+ current at positive potentials. Under these conditions as well, the maximal rates of rise of global myoplasmic Ca2+ transients were due primarily to Ca2+ release from the sarcoplasmic reticulum as revealed by effects of ryanodine and caffeine on the Ca2+ transients. Using such prepulses, linearity between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was found under a variety of pulse protocols. 4. Using one such pulse protocol, linearity between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was also found when Ca2+ currents assessed at one potential were reduced in magnitude during the onset of block by application of Co2+. Using the same pulse protocol, linearity between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was also found when use of Cs+ was avoided by blocking K+ currents with extracellular TEA and 4-aminopyridine. Linearity in the relationship between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was also found when Ca2+ transients were measured using the low affinity Ca2+ indicator Oregon Green 488 Bapta 5N in place of fluo-3. 5. These results appear to indicate that the cardiac ryanodine receptor is capable of being activated by only one calcium ion. Alternative interpretations of the data are discussed.}, address = {Department of Physiology \& Biophysics, University of Texas Medical Branch, Galveston, TX 77555-0641, USA.}, author = {Fan, J. S. and Palade, P.}, citeulike-article-id = {3023421}, citeulike-linkout-0 = {http://view.ncbi.nlm.nih.gov/pubmed/10200424}, citeulike-linkout-1 = {http://www.hubmed.org/display.cgi?uids=10200424}, day = {1}, issn = {0022-3751}, journal = {The Journal of physiology}, keywords = {activation, calcium, ion, of, receptor, ryanodine, ryr}, month = {May}, pages = {769--780}, posted-at = {2008-07-21 05:31:32}, priority = {2}, title = {One calcium ion may suffice to open the tetrameric cardiac ryanodine receptor in rat ventricular myocytes.}, url = {http://view.ncbi.nlm.nih.gov/pubmed/10200424}, volume = {516 ( Pt 3)}, year = {1999} }

TY - JOUR ID - citeulike:3023421 L3 - citeulike-article-id:3023421 N2 - 1. The release of Ca2+ from sarcoplasmic reticulum in response to Ca2+ entering through L-type Ca2+ channels was studied in isolated voltage clamped rat ventricular myocytes at room temperature using the fluorescent Ca2+ indicators fluo-3 and Oregon Green 488 Bapta 5N. 2. Depolarizations to positive potentials elicited fluo-3 Ca2+ transients with rates of rise that were linearly related to the magnitude of the peak measured Ca2+ current in the presence of Cs+-containing pipette solutions. 3. Further experiments utilizing prepulses to preactivate a constant number of channels also revealed a linear relationship between the Ca2+ transient rate of rise and the magnitude of entering Ca2+ current at positive potentials. Under these conditions as well, the maximal rates of rise of global myoplasmic Ca2+ transients were due primarily to Ca2+ release from the sarcoplasmic reticulum as revealed by effects of ryanodine and caffeine on the Ca2+ transients. Using such prepulses, linearity between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was found under a variety of pulse protocols. 4. Using one such pulse protocol, linearity between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was also found when Ca2+ currents assessed at one potential were reduced in magnitude during the onset of block by application of Co2+. Using the same pulse protocol, linearity between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was also found when use of Cs+ was avoided by blocking K+ currents with extracellular TEA and 4-aminopyridine. Linearity in the relationship between the Ca2+ transient rate of rise and the magnitude of the peak Ca2+ current was also found when Ca2+ transients were measured using the low affinity Ca2+ indicator Oregon Green 488 Bapta 5N in place of fluo-3. 5. These results appear to indicate that the cardiac ryanodine receptor is capable of being activated by only one calcium ion. Alternative interpretations of the data are discussed. JF - The Journal of physiology SN - 0022-3751 AD - Department of Physiology & Biophysics, University of Texas Medical Branch, Galveston, TX 77555-0641, USA. EP - 780 TI - One calcium ion may suffice to open the tetrameric cardiac ryanodine receptor in rat ventricular myocytes. VL - 516 ( Pt 3) SP - 769 KW - activation KW - calcium KW - ion KW - of KW - receptor KW - ryanodine KW - ryr AU - Fan, JS AU - Palade, P PY - 1999/05/01/ UR - http://view.ncbi.nlm.nih.gov/pubmed/10200424 ER -