Fig. 1. Voltage-clamp recordings from cells in acetate or biotin. The cells were held at resting potential (-30 mV) using two-electrode voltage-clamp. (A) Solid bars indicate application of 1 mmol l^-1 acetate. Lower two traces were recorded using K⁺-filled electrodes with 1 mmol l^-1 K⁺ in the bath. K⁺ currents were suppressed in the middle and upper traces using CsCl and tetraethylammonium (TEA), leaving Ca²⁺ (1 mmol l^-1) and Mg²⁺ (5 mmol l^-1) as the predominant charge carriers. Arrows show the outward conductances upon addition of acetate and removal of acetate. (B) Solid bars indicate application of variable concentrations of biotin at variable pH. K⁺ currents were suppressed in the middle and upper traces using CsCl and TEA leaving Ca²⁺ (1 mmol l^-1) and Mg²⁺ (5 mmol l^-1) as the predominant charge carriers. Arrows show the inward conductances upon removal of biotin.