Tracheobronchial irritancy of inhaled prostaglandins in the conscious cat

A novel test was developed to measure the tracheobronchial irritant activity of inhaled prostaglandins. Conscious restrained cats were challenged with separate aerosols of PGE1, PGF2alpha, acetylcholine or isoprenaline. All of the aerosols except isoprenaline caused coughing in a concentration related manner. Tolerance developed very quickly to the tracheobronchial irritation and lasted 1-2 days for PGE1 and less than 1 day for PGF2alpha and acetylcholine. When a 3 day interval between each aerosol challenge was used, PGF2alpha was approximately 700 times more potent than acetylcholine as a tracheobronchial irritant. The highest PGE1 aerosol concentration (500microgram/ml) also caused sedation, diarrhoea and salivation. This test probably provides a useful method for evaluating the tracheobronchial irritant activity of potential prostaglandin bronchodilator analogues and for investigating the mechanism of action of prostaglandin induced tracheobronchial irritancy.