Excitation—contraction coupling in amphioxus muscle cells
- 1 December 1971
- journal article
- Published by Wiley in The Journal of Physiology
- Vol. 219 (1), 233-251
- https://doi.org/10.1113/jphysiol.1971.sp009659
Abstract
1. Excitation-contraction coupling was studied in myotomal muscles of amphioxus, Branchiostoma californiense.2. The action potential of a muscle cell produces a twitch with a rise time of 30-40 msec at 11 degrees C and its Q(10) is about 2.2.3. The twitch increases in amplitude with increasing external Ca concentration and is abolished in Ca-free saline (1 mM-EGTA and 55.7 mM-MgCl(2)); the twitch amplitude is suppressed by Co or La ions.4. Caffeine at concentrations above 1 mM in the external saline causes a prolongation of the action potential and a contracture which lasts several minutes.5. After exposure to caffeine the responsiveness of the muscle to subsequent applications of caffeine recovers in normal saline in 20-30 minutes but not in Ca-free saline.6. The amplitude of the caffeine contracture is independent of the external Ca concentration and is unaltered after the twitch is eliminated in Ca-free saline.7. After exposure to caffeine a full-sized twitch can be obtained before the responsiveness to caffeine shows any significant recovery.8. It is concluded that the twitch is produced by the Ca influx resulting from the increased permeability of the muscle cell membrane to Ca during the action potential and that the Ca mobilized by caffeine is not necessary to the initiation of the twitch.9. Electronmicroscopy shows the existence of sarcoplasmic reticulum.Keywords
This publication has 19 references indexed in Scilit:
- Effects of Caffeine on Crayfish Muscle FibersThe Journal of general physiology, 1970
- The Intracellular Site of Calcium Activation of Contraction in Frog Skeletal MuscleThe Journal of general physiology, 1970
- Control of muscle contractionQuarterly Reviews of Biophysics, 1969
- Excitation-Contraction Coupling in a Barnacle Muscle Fiber As Examined with Voltage Clamp TechniqueThe Journal of general physiology, 1968
- The action of caffeine on the activation of the contractile mechanism in striated muscle fibresThe Journal of Physiology, 1968
- Calcium release and reabsorption in the sartorius muscle of the toadBiochemical and Biophysical Research Communications, 1966
- Effects of the Intracellular Ca Ion Concentration upon the Excitability of the Muscle Fiber Membrane of a BarnacleThe Journal of general physiology, 1966
- THE SARCOPLASMIC RETICULUM AND TRANSVERSE TUBULES OF THE FROG'S SARTORIUSThe Journal of cell biology, 1965
- The dependence of contraction and relaxation of muscle fibres from the crab Maia squinado on the internal concentration of free calcium ionsBiochimica et Biophysica Acta (BBA) - Specialized Section on Biophysical Subjects, 1964
- The relation between membrane potential and contraction in single crayfish muscle fibresThe Journal of Physiology, 1962