Regulation of vascular smooth muscle contraction by extracellular Na+

1. The effects of extracellular Na+ removal on agonist-induced contraction of vascular smooth muscle in vitro are reviewed. 2. The effects of extracellular Na+ removal on contraction vary depending upon the agonist and vessel. 3. Factors that may influence the effects of extracellular Na+ removal on agonist-induced contraction include the compound substituted for Na+, time of tissue exposure to lowered extracellular Na+, concentration of extracellular Na+, agonist concentration, presence of the vascular endothelium and presence of basal tone. 4. The potential influence of these factors needs to be determined and minimized, in studies that investigate the role of extracellular Na+ in agonist-induced contraction.