[Effect of gramicidin on the potassium conductance of an isolated frog muscle fiber].

The antibiotic gramicidin A (1.10(-6) M) increases the K+ conductance of normal and detubulated frog skeletal muscle fibres in isotonic K2SO4 solution to a steady-state level, which is reached in 6--9 min, and corresponds to 8058 +/- 1669 and 5767 +/- 902 Om-1. 10(-6)/cm2, resp. There is no correlation between the initial K+ conductance and the value of the steady state of gramicidin A-induced conductance (r = 0.24). According to the dimer hypothesis, the dissociation rate constant of the garmicidin channels was found to be 0.006 +/- 0.0001 sec-1. This result supports the suggestion of a higher stability of gramicidin channels in muscle compared to the bimolecular lipid membranes.