Single Influx Rate for 42K+ in the Single Fiber of the Barnacle

Abstract

The influx of 42K+ was measured in single muscle fibers of the giant barnacle Balanus nubilus. In influx experiments for 54 h, only one exchange component was evident for up to 90% intracellular K+. A comparison of this result with intracellular K+ activity measurements using K+-selective microelectrodes indicates at least 90% of the intracellular K+ is free in the myoplasm.