Effect of sensitization on membrane ion fluxes & intracellular calcium in guineapigs.

BACKGROUND & OBJECTIVES The biochemical mechanisms underlying the development of sensitization-induced airway hyperresponsiveness (AHR) in asthma are poorly defined. Alterations in the regulation of intracellular calcium may play an important role in its pathogenesis. We carried out this study to see the effect of sensitization with ovalbumin on membrane ion fluxes and intracellular calcium in a guinea pig model. METHODS Airway reactivity to inhaled histamine was measured initially and after sensitization with ovalbumin in 28 guineapigs. Intracellular calcium [Ca(2+)]i was measured in tracheal smooth muscle cells and peripheral leukocytes using fluorescent dye FURA 2AM. Calcium and sodium ion influx across the cell membrane was measured in leukocytes. Ouabain-sensitive Rubidium ((86)Rb) influx was measured in tracheal smooth muscles cells. The activities of Na(+), K(+) ATPase and Ca(2+) ATPase were measured in tracheal smooth muscle cells. Lipid peroxides were measured in plasma. RESULTS Airway responsiveness was significantly (P<0.001) increased after sensitization along with an increase in [Ca2+]i levels in leukocytes and tracheal smooth muscle cells, higher rates of (45)Ca and (22)Na influx in leukocytes and higher (86)Rb influx rates in tracheal smooth muscle cells, and increased levels of lipid peroxides in plasma. INTERPRETATION & CONCLUSION In guineapig model of asthma sensitization to allergen increased the membrane permeability to calcium and sodium, and intracellular calcium levels. These alterations may play a role in the pathogenesis of airway hyper-responsiveness following sensitization.