Mechanisms of the temperature effect on airway smooth muscle

We studied the effect of sudden cooling and warming on the contractile response of tracheal segments (TS) isolated from guinea pigs. After a standardized incubation period in normal physiological salt solution (PSS) (t degree = 37 +/- 0.5 degree C, pH = 7.34 +/- 0.02, PCO2 = 24 +/- 2 Torr, PO2 = 430 +/- 5 Torr) TS were quickly (20 sec) exposed to cool (24 degrees, 26 degrees, or 29 degrees C) PSS and changes in isometric force were measured using a Grass 0.03 transducer. Following the cooling period, maintained for 10-15 min, tissues were exposed to 34 +/- 0.5 degree C warm PSS and contractile response was measured again. It was found that: (1) quick cooling (24, 26 and 29 degrees C) induced a contraction of TS followed by a slow relaxation. The magnitude of the contraction was a function of temperature; the highest contraction was observed at 24 degrees C; (2) cooling, lower than 22 degrees C induced only a relaxation of TS; (3) quick warming of TS induced a biphasic response, i.e., a small relaxation followed by a slow, large contraction; (4) contraction as induced by cooling and relaxation as induced by warming were dependent on the initial length of the TS; (5) Cooling-induced contraction and warming-induced relaxation were inhibited with ouabain (10(-5) M); (6) Warming-induced contraction was attenuated with aspirin (50 micrograms/ml); but aspirin potentiated (P less than 0.001) cooling-induced contraction; (7) warming-induced contraction was inhibited with FPL 55712 (10(-6) M) (P less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)