The regulation of the intracellular sodium ion concentration in cultured chick embryo heart cells

Abstract

Using digital imaging microscopy with the fluorescent indicator sodium-binding benzofuran isophtalate, we examined the cytosolic Na + concentration ([Na +] i) in individual chick embryo heart cells. Inhibition of the Na +-H + exchanger using Na +-free (Li + substituted) medium and inhibition of the Na +-efflux through the Na +-Ca 2+ exchanger using Ca 2+-free medium didn't change the [Na +] i. The opening of voltage-dependent Na + channels with veratridine (150 μg/ml) and inhibition of the Na +-K +-Cl −-cotransporter with bumetanide (10 μM) led to an increase in [Na +] i by 107% and 86%, respectively, suggesting that the Na + channels and the Na +-K +-Cl − cotransporter predominantly regulate the [Na +] i in cultured chick embryo heart cells.