title: Mechanisms of the temperature effect on airway smooth muscle.
abstract: 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)
mesh_terms: D000818:Animals; D003080:Cold Temperature; D046508:Culture Techniques; D006168:Guinea Pigs; D006358:Hot Temperature; D007537:Isometric Contraction; D008297:Male; D009119:Muscle Contraction; D009126:Muscle Relaxation; D009130:Muscle, Smooth / Q000502:physiology*; D013696:Temperature; D013997:Time Factors; D014132:Trachea / Q000502:physiology*