DIETARY-SODIUM INTAKE, AIRWAY RESPONSIVENESS, AND CELLULAR SODIUM-TRANSPORT

Both epidemiologic and experimental evidence suggest that a high dieta ry sodium intake may increase airway responsiveness, but no adequate e xplanation exists of how changes in sodium intake might lead to increa sed responsiveness. This investigation was carried out to study dietar y sodium intake and airway response to methacholine in relation to cel lular sodium transport in 52 young men. Airway response to methacholin e was associated with urinary sodium excretion when subjects were on n ormal sodium intake. Airway responsiveness in patients with mild asthm a correlated with the furosemide-insensitive influx of sodium into per ipheral leukocytes stimulated by autologous serum, but there was no re lation between this influx and 24-h urinary sodium excretion. In a sep arate investigation, serum from subjects with increased airway respons iveness caused an increase in the sodium influx and sodium content of leukocytes from nonatopic subjects. The magnitude of the furosemide-in sensitive, serum stimulated influx was related to the degree of airway responsiveness of the serum donor, as was the increase in intracellul ar sodium content. Neither was related to the 24-h urinary sodium excr etion of the donor. Patients with airway hyperresponsiveness have an i ncreased sodium influx into cells stimulated by a serum-borne factor. This is independent of the effect of added dietary sodium on airway re sponsiveness.