Time and calcium dependence of activation and inactivation of calcium-induced release of calcium from the sarcoplasmic reticulum of a skinned canine cardiac Purkinje cell. Export

@article{citeulike:1181120, abstract = {Microprocessor-controlled changes of [free Ca2+] at the outer surface of the sarcoplasmic reticulum (SR) wrapped around individual myofibrils of a skinned canine cardiac Purkinje cell and aequorin bioluminescence recording were used to study the mechanism of Ca2+-induced release of Ca2+ from the SR. This Ca2+ release is triggered by a rapid increase of [free Ca2+] at the outer surface of the SR of a previously quiescent skinned cell. Ca2+-induced release of Ca2+ occurred under conditions that prevented any synthesis of ATP from ADP, was affected differentially by interventions that depressed the SR Ca2+ pump about equally, and required ionic conditions incompatible with all known Ca2+-releasing, uncoupled, partial reactions of the Ca2+ pump. Increasing the [free Ca2+]trigger up to an optimum increased the amount of Ca2+ released. A supraoptimum increase of [free Ca2+] trigger inactivated Ca2+-induced release of Ca2+, but partial inactivation was also observed at [free Ca2+] below that necessary for its activation. The amplitude of the Ca2+ release induced by a given increase of [free Ca2+] decreased when the rate of this increase was diminished. These results suggest that Ca2+-induced release of Ca2+ is through a channel across the SR membrane with time- and Ca2+-dependent activation and inactivation. The inactivating binding site would have a higher affinity for Ca2+ but a lower rate constant than the activating site. Inactivation appeared to be a first-order kinetic reaction of Ca2+ binding to a single site at the outer face of the SR with a Q10 of 1.68. The removal of inactivation was the slowest step of the cycle, responsible for a highly temperature-dependent (Q10 approximately 4.00) refractory period.}, author = {Fabiato, A.}, citeulike-article-id = {1181120}, citeulike-linkout-0 = {http://dx.doi.org/10.1085/jgp.85.2.247}, citeulike-linkout-1 = {http://www.jgp.org/cgi/content/abstract/85/2/247}, citeulike-linkout-2 = {http://view.ncbi.nlm.nih.gov/pubmed/2580043}, citeulike-linkout-3 = {http://www.hubmed.org/display.cgi?uids=2580043}, doi = {10.1085/jgp.85.2.247}, issn = {0022-1295}, journal = {J Gen Physiol}, keywords = {ca-trigger, canine, cicr-termination, purkinje-cell, serca, skinned-cell}, month = {February}, number = {2}, pages = {247--289}, posted-at = {2008-07-04 00:51:34}, priority = {0}, title = {Time and calcium dependence of activation and inactivation of calcium-induced release of calcium from the sarcoplasmic reticulum of a skinned canine cardiac Purkinje cell.}, url = {http://dx.doi.org/10.1085/jgp.85.2.247}, volume = {85}, year = {1985} }

TY - JOUR ID - citeulike:1181120 L3 - citeulike-article-id:1181120 N2 - Microprocessor-controlled changes of [free Ca2+] at the outer surface of the sarcoplasmic reticulum (SR) wrapped around individual myofibrils of a skinned canine cardiac Purkinje cell and aequorin bioluminescence recording were used to study the mechanism of Ca2+-induced release of Ca2+ from the SR. This Ca2+ release is triggered by a rapid increase of [free Ca2+] at the outer surface of the SR of a previously quiescent skinned cell. Ca2+-induced release of Ca2+ occurred under conditions that prevented any synthesis of ATP from ADP, was affected differentially by interventions that depressed the SR Ca2+ pump about equally, and required ionic conditions incompatible with all known Ca2+-releasing, uncoupled, partial reactions of the Ca2+ pump. Increasing the [free Ca2+]trigger up to an optimum increased the amount of Ca2+ released. A supraoptimum increase of [free Ca2+] trigger inactivated Ca2+-induced release of Ca2+, but partial inactivation was also observed at [free Ca2+] below that necessary for its activation. The amplitude of the Ca2+ release induced by a given increase of [free Ca2+] decreased when the rate of this increase was diminished. These results suggest that Ca2+-induced release of Ca2+ is through a channel across the SR membrane with time- and Ca2+-dependent activation and inactivation. The inactivating binding site would have a higher affinity for Ca2+ but a lower rate constant than the activating site. Inactivation appeared to be a first-order kinetic reaction of Ca2+ binding to a single site at the outer face of the SR with a Q10 of 1.68. The removal of inactivation was the slowest step of the cycle, responsible for a highly temperature-dependent (Q10 approximately 4.00) refractory period. IS - 2 JF - J Gen Physiol SN - 0022-1295 EP - 289 TI - Time and calcium dependence of activation and inactivation of calcium-induced release of calcium from the sarcoplasmic reticulum of a skinned canine cardiac Purkinje cell. VL - 85 SP - 247 KW - ca-trigger KW - canine KW - cicr-termination KW - purkinje-cell KW - serca KW - skinned-cell AU - Fabiato, A PY - 1985/02// UR - http://dx.doi.org/10.1085/jgp.85.2.247 ER -