EFFECT OF POTASSIUM ON "RESTING" POTENTIAL AND RESPIRATION OF CRAB NERVE

Abstract

The effect on crab leg nerve (Grapsus grapsus and Libinia emarginata) of increasing or decreasing the extracellular KC1 has been studied without altering the concn. of any of the other ionic constituents of an artificial sea water medium. This is necessary if damage from swelling, resulting when K replaces sodium, is to be prevented. Under these conditions the "potassium" potential of the nerves decreases linearly with an increase of the logarithm of the extracellular K concn. (Ko) except at very low and very high values of Ko. The potentials recover better from strong K solns. in which KCl is present in addition to the usual NaCl than when it replaces the latter. The respiration of Libinia leg nerves is maximal for a Ko of 30 mM /1., and is reduced by lower or higher conens. The effect of Ko on the max. change in potential during anoxia (i.e., the anoxia sensitivity) depends on the volume of soln. in contact with the fibers. With large volumes it resembles that on respiration, but the max. sensitivity lies between 10 and 15 mM/1. With small volumes the sensitivity decreases rapidly with increasing Ko. These observations suggest the release of K by the fibers during anoxia and its reabsorption during recovery in oxygen.