Sheep were classified on the basis of their airway response to Ascaris suum antigen aerosols as allergic or nonsensitive. Allergic sheep were classed as acute or dual responders. Acute responders had only an immediate increase in mean airflow resistance after antigen, whereas dual responders had an immediate and late-phase (6-8 h after antigen challenge) increase in mean airflow resistance; nonsensitive sheep had minimal airway responses to antigen (< 30% increase from base line). The sheep were anesthetized 2 wk later and, after a left thoracotomy, were challenged with antigen to determine bronchial vascular responses; bronchial artery blood flow was measured with an electromagnetic flow probe. Airway responses to antigen aerosol challenge were similar in the anesthetized and conscious animals. The mean fall in bronchial vascular resistance (BVR) immediately after antigen challenge was similar in acute and dual responders (41 ± 7 and 47 ± 9% of base line, respectively). In dual responders, late-phase airway responses were preceded by a significant increase from base line in Q̇br and a fall in bronchovascular resistance (BVR). The mean fall in BVR 6-8 h after antigen challenge in documented dual responders was significantly different from bronchial vascular responses in acute responders (59 ± 3 vs. 89 ± 10%, respectively). Sheep without airway responses to A. suum had no significant changes in bronchial hemodynamics or airways mechanics. Late-phase-associated changes in BVR are a specific response to antigen challenge and may be a sensitive index of mediators being released. We hypothesize that late-phase-associated changes in BVR may contribute to the increase in mean airflow resistance during late-phase responses by promoting edema formation.
- Ascaris suum
- bronchial artery blood flow
- immediate hypersensitivity
- late-phase allergic responses
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation