The e effect o of p prolonged e exposure tto N NO 2 from b birth o on a airways responsiveness iin rrabbits s sensitized a at b birth

ABSTRACT: Our aim was to determine whether daily exposure to 4 ppm nitrogendioxide (NO 2 ) from birth until 3 months of age influenced the development of airwayshyperresponsiveness and atopic sensitivity in immunized rabbits.Littermate New Zealand White (NZW) rabbits were immunized within 24 h ofbirth by i.p . injection of house dust mite antigen in Al(OH) 3 gel, and exposed toeither ambient air or 4 ppm NO 2 for 2 h·day -1 , 5 days·week -1 . At 3 months, bron-choalveolar lavage (BAL) and serum samples were obtained. Airways responsive-ness was measured as the provocative concentrations (mg·ml -1 ) of histamine ormethacholine required to elicit a 50% increase in airway resistance (R L PC 50 ) anda 35% decrease in dynamic compliance (CdynPC 35 ).There were no differences in total cell or differential cell counts recovered in BALfluid between control and NO 2 exposed animals. Airways responsiveness did notdiffer between groups of animals (histamine R L PC 50 values: air (n=15) versus