Almitrine mesylate, a peripheral chemoreceptor agonist, inhibits selectively the Ca2+-dependent K+ channel.
Almitrine inhibits the activity of a high-conductance (152±13 pS), Ca2+-dependent K+ channel by decreasing its open probability. The IC50 value of the effect is 0.22 μM. The inhibitory effect of Almitrine on Ca2+-dependent K+ channels also is observed in GH3 cells. Almitrine at concentrations up to 10 μM does not affect whole-cell voltage-dependent K+, Ca2+, or Na+ currents in rat or rabbit cells. However, this concentration of Almitrine significantly inhibits the Ca2+-dependent component of K+ currents in rat chemoreceptor cells[1].
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[2].
[1]. López-López JR, et al. Effects of Almitrine bismesylate on the ionic currents of chemoreceptor cells from the carotid body. Mol Pharmacol. 1998 Feb;53(2):330-9. [2]. Bee D, et al. An analysis of the action of an analogue of Almitrine bismesylate in the rat model of hypoxic lung disease. Exp Physiol. 1992 Nov;77(6):819-28.