Effects of cooling on in vitro responses of human peripheral airways to inflammatory mediators and neurotransmitters.

In asthma, inhalation of cold dry air induces bronchoconstriction. It has been suggested that cooling of the airway wall might induce this bronchoconstriction. Therefore the effects of cooling on the contractility of human peripheral airways were studied in vitro before and during lowering of the temperature. Cooling relaxed human airways in vitro and reduced responsiveness to methacholine, histamine and LTC4 both in terms of -logEC50 and maximal effect. It also reduced the maximal effect of isoprenaline. There was no measurable alpha-adrenergic activity before or during cooling. We conclude that cooling does not sensitize human airways to any of these agonists and that cold-induced bronchoconstriction in vivo is not due to a direct effect of cooling on airway smooth muscle.