Late-phase bronchial vascular responses in allergic sheep

Area of Science:

• Pulmonary immunology
• Respiratory physiology

Background:

• Allergic sheep models are used to study airway hyperresponsiveness.
• Ascaris suum antigen challenge elicits immediate and late-phase airway responses in sensitive sheep.

Purpose of the Study:

• To investigate bronchial vascular responses during immediate and late-phase airway reactions to Ascaris suum antigen in sheep.
• To differentiate bronchial vascular resistance (BVR) changes in acute versus dual responders.

Main Methods:

• Sheep were classified as allergic (acute or dual responders) or nonsensitive based on airway response to Ascaris suum antigen aerosol.
• Bronchial artery blood flow was measured using an electromagnetic flow probe in anesthetized sheep after antigen challenge.
• Bronchial vascular resistance (BVR) was calculated and analyzed during immediate and late-phase responses.

Main Results:

• Both acute and dual responders showed an immediate fall in BVR post-antigen challenge.
• Dual responders exhibited a significant fall in BVR during the late phase (6-8 h) after antigen challenge, unlike acute responders.
• Nonsensitive sheep demonstrated no significant changes in airway mechanics or bronchial hemodynamics.

Conclusions:

• Late-phase bronchial vascular resistance changes are specific to antigen challenge in dual responders.
• Bronchial vascular resistance dynamics may serve as a sensitive indicator of mediator release in allergic airway responses.