Recovery time course of airway hyperresponsiveness to acetylcholine after ovalbumin challenge in guinea pigs.

Abstract

Sequential changes in airway and adrenergic responsiveness after ovalbumin (OA) challenge were studied in guinea pigs. Airway responsiveness, alpha 1- and beta-adrenoceptor numbers and adenylate cyclase activity was determined after increasing doses of acetylcholine aerosol were administered before, 0, 3, 7, and 14 days after exposure to 2 percent OA or physiologic saline solution for 10 consecutive days. The antiasthmatic agent, azelastine (1 mg/kg/day, intraperitoneal), was administered for 14 days after the tenth exposure to OA in some animals. Airway responsiveness increased significantly after OA exposure, beta-adrenoceptor numbers decreased by 35 percent, and adenylate cyclase activity decreased by 54 percent (p less than 0.01). Values remained significantly different than control animals for 7 days and required 14 days to normalize completely. Azelastine decreased the recovery period to seven days. Azelastine may affect airway responsiveness, at least in part, by increasing beta-adrenergic responsiveness.