DISTRIBUTION OF INORGANIC IONS IN LOBSTER MUSCLE

Compartmentation of intracellular chloride (Cli-) in muscle of lobster walking leg was shown by two independent methods: (1) after equilibration in low-Cl- medium, Cli- was reduced from 85 to 30 mM/kg cells; (2) after equilibration in medium containing 36Cl, a similar concentration of Cli-, 32.5 mM/kg cells, remained unexchanged with the isotope. The Cl- remaining in muscles in low-Cl- medium was essentially nonexchangeable, showing that the immobile compartment of Cli- is independent of changes in the mobile compartment of Cli- and of the external concentration of Cl-. The mobile compartment varied linearly with external Cl-, with a constant ratio of about 10:1. Sodium appeared to be distributed similarly to chloride, both qualitatively and quantitatively. From experiments on the relation between external K+ concentration and the resting membrane potential, and on the exchangeability of intracellular K+, the possibility of compartmentation of Ki+ is discussed. © 1968.