K ⁺ channel

Almitrine inhibits the activity of a high-conductance (152±13 pS), Ca ²⁺ -dependent K ⁺ channel by decreasing its open probability. The IC ₅₀ value of the effect is 0.22 μM. The inhibitory effect of Almitrine on Ca ²⁺ -dependent K ⁺ channels also is observed in GH3 cells. Almitrine at concentrations up to 10 μM does not affect whole-cell voltage-dependent K ⁺ , Ca ²⁺ , or Na ⁺ currents in rat or rabbit cells. However, this concentration of Almitrine significantly inhibits the Ca ²⁺ -dependent component of K ⁺ currents in rat chemoreceptor cells.

Almitrine acts via the peripheral arterial chemoreceptors raising carotid sinus nerve output and minute ventilation. Almitrine also has a pulmonary vascular action causing a dose-dependent constriction and dilatation. At low doses Almitrine enhances hypoxic pulmonary vasoconstriction and may improve the overall ventilation/perfusion ratio.