Pulmonary Function Analysis in the Rabbit Following Bronchochallenge to Causative Agents and Mediators of the Acute Byssinotic Response

Abstract

New Zealand White rabbits were acutely bronchochallenged for 5 min to ascertain airway responsiveness with six potential byssinogenic agents and mediators: 0.1 g/mL cotton dust extract (CDE), 0.1 g/mL cotton bract extract (CBE), 1 mg/mL endotoxin, 1 mg/mL n-formyl methionyl peptide (n-fMet), 10 mg/mL 5-hydroxytryptamine (5-HT), and 1 mg/mL prostaglandin F2 alpha (PGF2 alpha). Methacholine (MC), 10 mg/mL, was used as a control bronchoconstrictor. Clinically objective criteria were established using increases in resistance values compared to those obtained with saline controls. Animals were classified as: mild responders (Mi) = 125-149%; moderate responders (Mo) = 150-199%; or severe responders (S) = greater than 200%. Three of five (2Mo, 1S) rabbits showed increased pulmonary resistance to CDE bronchochallenge, 3/5 (1Mi, 1Mo, 1S) to CBE, 1/5 (Mo) to purified endotoxin, 4/5 (1Mo, 3S) to n-fMet, 3/5 (1Mi, 1Mo, 1S) to 5-HT, and 2/5 (1Mo, 1S) to PGF2 alpha. All five rabbits (1Mo, 4S) responded to MC bronchochallenge. Rabbits responded minimally to saline, the common solvent of all test agents; however, when challenged with methacholine, a known bronchoconstrictor, rabbits showed significant overt symptoms of acute respiratory distress with immediate and substantial increases in resistance over saline controls. CDE, CBE, and n-fMet inhalation challenge resulted in a majority or all animals showing increased resistance. 5-HT contained in CDE and CBE, exhibited similar resistance increases; however, endotoxin, also found in cotton dust, showed little airway reactivity. The rabbit is useful for characterizing changes in pulmonary function parameters seen in the acute byssinotic reaction. This study has demonstrated that bronchochallenge in the rabbit with potential byssinogenic agents (CDE, CBE, endotoxin, and n-fMet) and mediators (5-HT and PGF2 alpha) result in measurable changes in airway function, particularly increased resistance. Since bronchoconstriction is the major clinical manifestation of the acute byssinotic reaction in man and animals, it is likely that bronchoconstriction observed in cotton mill workers may be in part or totally the result of inherent dust constrictor substances or secondarily released mediators.