Arsenazo III Ca2+-transients of Xenopus skeletal muscle during repetitive stimulation in hypertonic solution

The arsenazo III Ca2+-transients (AZ signals) were measured in hypertonic solution. The muscle fiber of Xenopus was stimulated at the frequency of 0.1/s. The AZ signal responding to the first stimulus in hypertonic Ringer solution was nearly similar to that in normal Ringer solution. After 8 repetitive stimuli, however, time to peak was increased to 3 times and decay time constant was up to 4 times as long as the control. The apparent inhibition of Ca2+ uptake into sarcoplasmic reticulum was supposed to be the origin of the prolongation in time to peak and decay time course.