Effects of amphotericin B on the electrical properties and electrolyte content of frog sartorius muscle.

We studied the effect of amphotericin B (52 microM) on the membrane potential, membrane resistance, and intracellular Na+ and K+ concentrations in isolated frog sartorius muscles to characterize further the nature of the ionic conductance induced by the antibiotic. After 5 h of exposure to amphotericin B, the membrane depolarized from -89.9 to -51.0 mV, the membrane resistance decreased from 4537 to 907 omega cm2, [K]i decreased from 122 to 31.2 mmol/L fiber H2O, and [Na]i increased from 30.9 to 88.7 mmol/L fiber H2O. The relative sodium permeability, PNa/PK, calculated with the Goldman equation remained apparently constant at a value of 0.01 in treated and untreated muscles. We hypothesize that amphotericin B creates either a nonselective cation channel or a completely nonselective ionic leak channel whose equilibrium potential is equal or close to the membrane potential.