Sodium is the primary cation (positive ion) in extracellular fluids in animals and humans. Sodium ions are necessary for regulation of blood and body fluids, transmission of nerve impulses, heart activity, and certain metabolic functions. Physiologically, it exists as an ion in the body. Sodium is needed by animals, which maintain high concentrations in their blood and extracellular fluids, but the ion is not needed by plants. The human requirement for sodium in the diet is less than 500 mg per day, which is typically less than a tenth as much as many diets "seasoned to taste. " Most people consume far more sodium than is physiologically needed. For certain people with salt-sensitive blood pressure, this extra intake may cause a negative effect on health.

Uridine 5'-triphosphate (UTP, INS316) is a naturally occurring agonist for P2Y(2) receptors on the apical surface of ciliated respiratory epithelium. INS316, being developed by Inspire Pharmaceuticals, is a short-acting, aerosolized uridine 5-triphosphate (UTP) solution used as a diagnostic aid for lung cancer. INS316 appears to improve sputum expectoration mediated through the P2Y2 receptor, a nucleotide receptor expressed in human airway epithelial cells and some other tissues. UTP binding to the P2Y2 receptor triggers signal transduction that leads to chloride ion secretion, thereby resulting in mucociliary clearance of airway. UTP stimulates salt and water transport and cilia beat frequency in human airway epithelium in vitro. Single, inhaled doses of UTP stimulate mucociliary clearance in conscious, intubated sheep and in patients with mild chronic bronchitis (smokers and former smokers), suggesting that UTP may be useful for obtaining deep-lung sputum specimens suitable for diagnostic purposes. A single dose of INS316 safely improves the ability of patients with mild chronic bronchitis to expectorate a deep-lung sputum specimen suitable for cytologic evaluation.

Uridine 5'-triphosphate (UTP, INS316) is a naturally occurring agonist for P2Y(2) receptors on the apical surface of ciliated respiratory epithelium. INS316, being developed by Inspire Pharmaceuticals, is a short-acting, aerosolized uridine 5-triphosphate (UTP) solution used as a diagnostic aid for lung cancer. INS316 appears to improve sputum expectoration mediated through the P2Y2 receptor, a nucleotide receptor expressed in human airway epithelial cells and some other tissues. UTP binding to the P2Y2 receptor triggers signal transduction that leads to chloride ion secretion, thereby resulting in mucociliary clearance of airway. UTP stimulates salt and water transport and cilia beat frequency in human airway epithelium in vitro. Single, inhaled doses of UTP stimulate mucociliary clearance in conscious, intubated sheep and in patients with mild chronic bronchitis (smokers and former smokers), suggesting that UTP may be useful for obtaining deep-lung sputum specimens suitable for diagnostic purposes. A single dose of INS316 safely improves the ability of patients with mild chronic bronchitis to expectorate a deep-lung sputum specimen suitable for cytologic evaluation.