The membrane potential and permeabilities of the L cell membrane to Na, K and chloride.

1. The chloride content and fluxes, and the membrane potential of L cells have been measured.2. L cells contain chloride, 70 m-mole/l. intracellular water and have a flux of 5.5 p-mole/cm(2) sec.3. The membrane potential is -15 mV.K-free Krebs causes an increase in E(m) and replacing chloride with sulphate causes a temporary reduction in E(m).4. These values for E(m) and chloride, and previously obtained values for Na and K fluxes and contents were used to calculate the permeabilities of the various ions using the Goldman constant field theory. This gave permeabilities of 6.3, 4.2 and 51 x 10(-9) cm/sec for K, Na and chloride respectively, a ratio of 1:0.67:8.10.5. It is concluded that these cells have a low membrane potential because the P(K) is some 100 times lower than in skeletal muscle, therefore leading to a P(K) of the same order as P(Na).