Abstract
Tetraethylammonium (TEA, 2.5-10 mM) caused a marked increase in the negative afterpotential of frog sartorius muscle fibers bathed in hypertonic medium. By contrast, TEA (5-10 mM) depressed the late negative afterpotential produced by repetitive stimulation at a rate of 50 Hz for 150 msec. Both actions of TEA were attributed to a decrease by TEA of potassium efflux from the muscle fibers. The depression by TEA of the late negative afterpotential was attributed to an action of TEA on the transverse tubules. Measurements of the influx and efflux of isotopic potassium (K42) in resting muscles in hypertonic medium showed that TEA (5-20 mM) depressed both the influx and efflux of K42. Since the flux ratio (efflux/influx) was depressed by TEA, the efflux of K42 appeared to be more sensitive to blockade by TEA than was influx.
Footnotes
- Received August 4, 1969.
- Accepted November 29, 1969.
- © 1970, by The Williams & Wilkins Co.
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