Sensitivity to H, Li and Mg ions of the slow inward sodium current in frog atrial fibres

摘要: Abstract Membrane currents have beenmeasured in frog atrial fibres under voltage clamp conditions (double sucrose gap method); the effects on these of (i) an increase [H]o, (ii) complete substitution external Na by Li, (iii) addition Mg been studied. The TTX-sensitive rapid inward current is decreased acid Ringer (pH 5.6) as compared to values normal 7.8); it unchanged Li-Ringer and increased Mg-Ringer. slow calcium (measured TTX, Na-free solution) Mg-Ringer Li-Ringer. Increases or decreases affecting sodium never exceed 40% are generally smaller. On other hand Ca-free always suppressed three participation ions so called Ringer, that Mg-free discussed. Indirect evidences presented favour such a participation. After 1.8 m carried only Ca ions. Since increases markedly concluded conductance controlled both being strongly pH-dependent. It also suggested participating do not penetrate necessarily through same channel.