[Temperature dependence of bronchial and tracheal reactivity of isolated respiratory tract preparations of the guinea pig].

The intrapulmonary loss of heat due to hyperventilation may be considered as essential pathogenetic factor in producing exercise induced asthmatic response. The temperature dependence of smooth muscle contraction was investigated using isolated trachea and isolated lung strips of guinea pigs. The measurements of the contraction responses to cumulative dose administrations of acetylcholine (10(-9) to 10(-3) M) were made in thermostated organ baths (isotonic contraction, modified Krebs-Henseleit solution, pH 7.4, air gassing). The standardized measurement data were adjusted to a non-linear function with the aid of a computer. The reactivity of the isolated trachea remained unchanged with a change of the bath temperature (from 37 degrees C to 30 degrees C), whereas a markedly increased contraction response to acetylcholine was observed in the lung strips. The results indicate that the contraction induced by the drop in temperature is localized in the small airways. The stabilization of reactive oxygen metabolites as an asthma-inducing mechanism is discussed as a possible explanation of the temperature-dependent effects.