Figure 2.

Basic properties and Ba²⁺ sensitivity of endogenous Kir current in porcine BM-SP cells. (A) Comparison of Kir currents recorded at low (6 mM) and high (156 mM) extracellular [K⁺] solutions in the same cell. Note a shift in the reversal potential from −79 to −2 mV. (B) Kir current recorded in a single SP cell at 0, 0.5, 5, 10, and 300μM extracellular Ba²⁺. (C) Concentration dependence of Ba²⁺ block. Fractional block was determined at −100 mV and calculated as (I_control − I_Ba²⁺)/I_control, where I_control is the current recorded before application of Ba²⁺ and I_Ba²⁺ is the current recorded at a specific Ba²⁺ concentration. Each point is the mean ± SE (n = 5). The data were fitted with the function I_Ba²⁺/I_control = 1/(1 + [Ba²⁺]/K_d) where K_d is the dissociation constant.