Characterization of a late phase pulmonary response after antigen challenge in allergic sheep

We determined if allergic sheep undergo a dual bronchoconstriction in response to inhalation of antigen and whether these responses could be modified by cromolyn or glucocorticosteroids. In 8 conscious sheep with Ascaris suum hypersensitivity, mean pulmonary flow resistance (RL), dynamic lung compliance (Cdyn), thoracic gas volume (Vtg), and arterial oxygen tension (Pao2) were determined prior to, immediately after, and from 2 through 8 h after and 24 h after inhalation challenge with Ascaris suum antigen. Immediately after antigen challenge, mean specific lung resistance (SRL = RL·Vtg) increased by 750% (p < 0.01) and mean Cdyn and PaO2 decreased by 55% (p < 0.01) and 37% (p < 0.01), respectively. By 5 h after challenge, mean SRL and Pao2 had returned to baseline values, whereas mean Cdyn was still below baseline (-19%, p < 0.05). At 6.5 h, mean SRL increased again to 245% (p < 0.01) of baseline and remained significantly elevated through the eighth hour. The average increase in mean SRL for the 6.5- to ...