Determination of the role of na+/ca2+ exchanger system in the relaxant effect of motherwort (Leonurus turkestanicus) extract

Abstract

The Na+/Ca2+ exchanger (NCX1) is critical for the regulation of contraction and relaxation in vascular smooth muscle cells, particularly in the rat aorta. Under standard conditions in Krebs physiological solution, the concentration of Na+ ions is typically maintained at 118 mM. However, when Na+ concentration is reduced to 25 mM or replaced with choline chloride, a marked contraction occurs, likely due to an increase in intracellular Ca2+ concentration facilitated by the Na+/Ca2+ exchange system. In these experiments, Na+ in the Krebs solution was replaced with choline chloride to investigate this response. After removing the endothelium, an initial contraction was induced in normal Krebs solution, followed by a wash and a 30-minute incubation in Krebs solution with 1.18 mM choline chloride replacing NaCl. This modification led to a progressively increasing contraction, hypothesized to result from Ca2+ ion entry through the Na+/Ca2+ exchanger. These findings underscore the role of Na+/Ca2+ exchange in smooth muscle cell contraction by illustrating how variations in Na+ concentration can influence Ca2+ influx, providing insights into cellular ion exchange mechanisms and their influence on vascular tone.