Increased bronchovascular permeability after allergen exposure in sensitive asthmatics

To investigate the possibility that an increase in bronchovascular permeability is associated with allergen exposure in sensitive asthmatics we evaluated the amounts of serum proteins in bronchoalveolar lavage (BAL) effluents before and after local challenge with allergen. After exposure of sensitive asthmatic airways (n = 15) to allergen significant increases in total protein compared with controls were observed: 0.08 +/- 0.01 mg/ml in control airways and 0.13 +/- 0.02 mg/ml in challenged airways; P less than 0.05. The greatest changes induced by allergen exposure involved small-molecular-weight proteins (less than 345,000) and an inverse correlation was observed between log molecular weight and percent increase in the concentrations of the specific proteins; r = -0.61. BAL-serum distribution coefficients of serum proteins in airway fluids reflected a greater diffusability of low-molecular-weight proteins immediately after allergen exposure. We also evaluated the movement of serum proteins into lung after local allergen exposure using intravenously administered 99mTc-albumin (n = 10) and found an immediate 3.8-fold increase in amounts of radioactive albumin in allergen exposed airways compared with airways exposed to diluent. Most of the radioactivity was recovered in the first 5 ml of aliquot withdrawn, suggesting a marked increase in the permeability of the bronchial (large airway) vascular-epithelial membrane. An increase in serum proteins was also observed in BAL fluid of asthmatics 2-4 h after aerosol challenge (n = 4), including all proteins in the molecular weight range 45,000-900,000. These studies suggest that allergen exposure in sensitive asthmatics causes an acute increase in bronchovascular permeability to serum proteins.