[Gramicidin A-induced membrane conductance of isolated muscle fiber]

The conductance of single fibres from m. ileofibularis of Rana esculenta was studied in isotonic K2SO4 solution under constant--current conditions using the double sucrose gap method. The antibiotic gramicidin A effects a drastic increase of membrane conductance. Variation of the gramicidin-induced conductance with gramicidin concentration in the bathing solution (10(-8)-5,5 . 10(-7) M) was investigated. Gramicidin-induced conductance was proportional to the square of gramicidin concentration in the solution, as expected in a channel made of gramicidin dimer.