Magnesium and chloride “permeations” in muscle

Abstract

The Mg content of the frog''s sartorius (Rana temporaria), as detd. by the hydroxy-quinoline method, is 26.8 [plus or minus] 0.6 mg./100 g. (35 detns). The Mg content after 1-5 days immersion in Mg free Ringer is 22.3 [plus or minus] 1.0 mg./100 gm. (8 detns.). Over the long period of retention Mg enters freely, reaching a "permeation" of about 100 in 24 hrs., the total Mg being then much higher than in the external fluid. By "permeation" is here meant the amount per 100 gm. of tissue water as a percentage of the external concn. It is concluded that the Mg in normal muscle is bound to 80-90% of the total present. For short period immersions at room temp. Mg enters the frog''s sartorius much more slowly than does chloride, the "permeation" of the free Mg ion being only 1/3-1/2 that of the chloride after 90 min. The chloride "space'' cannot therefore be merely the interspaces between the tissue elements with free diffusion therein of external electrolytes.