NONSPECIFIC AIRWAY HYPERREACTIVITY IN ISOLATED RESPIRATORY PREPARATIONS FROM GUINEA-PIGS SENSITIZED AND CHALLENGED WITH OVALBUMIN

Airway hyperreactivity to physical, chemical, immunological and pharma cological stimuli is well documented in vivo. The aim of this study wa s to investigate whether tissues taken from guinea-pigs that had been shown to display hyperreactivity in vivo after antigen challenge were also hyperreactive in vitro. Isolated airway-perfused lungs from ovalb umin-sensitized guinea-pigs challenged 24 h beforehand with an aerosol of ovalbumin showed a significant (P<0.05) increase in responsiveness to the bronchoconstrictor response to a bolus dose of carbachol (10 m u g) when compared with saline challenged animals. The contractile res ponses to single doses of carbachol (10 mu g) and histamine (30 mu g) in immersed tracheal spiral preparations taken from sensitized animals exposed to the ovalbumin were also significantly enhanced (P<0.05). A non-significant leftward shift was observed in the concentration-resp onse curve for histamine in challenged perfused lungs from ovalbumin-c hallenged animals compared with an NaCl challenge. Concentration-respo nse curves to carbachol and histamine in immersed tracheal spirals wer e virtually superimposed. Therefore, this study has shown non-specific airway hyperreactivity of isolated airway perfused lungs at 24 h foll owing a challenge of sensitized guinea-pigs with aerosolized ovalbumin , although this was not evident from concentration-response curves in immersed trachea. The isolated perfused lung therefore provides a simp le method for further evaluation of the mechanisms of airway hyperreac tivity.