AJP - Cell Physiology, Vol 233, Issue 1 19-C24, Copyright © 1977 by American Physiological Society
Prolonged potentials in gastrointestinal muscles induced by calcium chelation
C. L. Prosser, D. L. Kreulen, R. J. Weigel and W. Yau
When stomach muscles of skate, toad, or frog or intestinal muscle of cat
are treated with Ca-free physiological solutions containing 2-5 mM EGTA or
EDTA, spontaneous spikes and slow waves disappear reversibly. With
continued treatment, depolarization of 25-30 mV from resting potentials of
-65 mV occurs and rhythmic prolonged potentials of several seconds duration
appear. They show rapid depolarization to near zero and rapid
repolarization and they may continue for several hours. The prolonged
potentials disappear when Na is replaced by Li, Tris, or choline. They are
insensitive to TTX. The EGTA-induced waves are abolished by Mn, Co, La,
verapamil, and D 600. After 10-15 min in 5 mM EGTA, voltage-current and
abolition of anomalous rectification. It is concluded that when bound Ca is
removed by a chelator, nonspecific reduction in resistance occurs and Na
ions may enter rhythmically through channels normally used by Ca.
