BRONCHIAL RESPONSIVENESS TO INHALED HISTAMINE IN CANINE PULMONARY CONGESTION

To elucidate the role of bronchial hyperresponsiveness (BHR) in pulmon ary congestion, an inhaled histamine provocation test was performed in dogs with acute pulmonary congestion, and the role of vagal nerve act ivity and arachidonic acid metabolites on bronchial responsiveness was evaluated. We assessed BHR with the provocation concentration of hist amine causing a 100% increase in pulmonary resistance (PC100) in an op en-chest anesthetized and tracheotomized canine model before and after left atrial balloon inflation. Twenty-two mongrel dogs (8-14 kg) were anesthetized with sodium thiopental (15-20 mg/kg) and mechanically ve ntilated with positive end-expiratory pressure at 3 cmH(2)O. A Foley c atheter was inserted into the left atrium to cause pulmonary congestio n, in which mean left atrial pressure was increased to 18 mmHg, In 6 d ogs, histamine provocation was examined before and after pulmonary con gestion was effected. Intravenous indomethacin (1 mg/kg) administratio n and vagotomy were performed in 5 dogs. In pulmonary congestion, PC10 0 was significantly decreased both before and after vagotomy and after indomethacin administration. We conclude that pulmonary congestion au gments bronchial responsiveness to inhaled histamine and that neither vagotomy nor indomethacin administration prevents bronchial hyperrespo nsiveness in pulmonary congestion. These findings suggest that bronchi al hyperresponsiveness in pulmonary congestion is related to another f actor such as bronchial edema.