ELECTROLYTES IN NERVE

Abstract

Frog nerves were soaked for varying periods in different solns. and subsequently analyzed for Na, K, chloride and bicarbonate. Nerves lose K to the soln. when the conc. is less than 2 milli-equivalents (m.-eq.) % K in March frogs and less than 0.5 m.-eq. % K in Nov. frogs. In solns. of higher conc. K diffuses into the nerves in spite of the higher conc. inside. The K content of nerves is 4.8 m.-eq. % in March and 3.02 milli-equivalents % in Nov. The pH inside the nerve fibers in vivo is more acid than that outside, but tends to become equal after soaking in Ringer''s soln. It becomes more acid after soaking in an acid soln. and more alkaline in an alkaline soln. The chloride content of the nerve varies with that of the soln., being 50% of that outside in the normal nerve and 57% in soaked nerves. Chloride readily exchanges with other anions in the soln. and is presumably located outside the nerve fibers. Most of the Na behaves like chloride, but the Na in excess of the chloride seems more firmly fixed in the nerve and is possibly retained inside some of the cells. While soaking in Ringer''s soln. K is lost, partly in exchange for Na, while chloride is gained, probably in exchange with some other anions previously present or formed in metabolism. Chloride and most of the Na readily escape from nervea immersed in isotonic sugar soln., while the K is relatively indiffusible. According to a tentative distribution of the electrolytes between the inside and outside of the fibers of frog nerve suggested, ca. 36% of the weight of the nerve is "K space" and the rest "NaCl space." There appears to be a large excess of inorganic cations over anions in the K space. In lobster and crab nerves, ca. 25% of the weight of the nerve contains Na and Cl in conc. equal to those outside. The rest of the nerve probably contains most of the K in conc. 12-15 times as great as that outside. As K is lost from the crab and lobster nerves they gain in Na, Ca and chloride. The gain in chloride is particularly marked and probably occurs in exchange with some other undetermined anions originally present.