The direct effect of temperature on airway smooth muscle

We tested the hypothesis that temperature may directly influence the resting membrane potential (Em), (Na+ + K+)-ATPase activity, and the contractile response to histamine of bovine and guinea pig airway smooth muscle. To determine the resting membrane potential of airway smooth muscle, glass microelectrodes filled with 3M KCl were used. As a measure of (Na+ + K+)-ATPase activity, potassium-induced relaxation was used employing the method of Webb and Bohr (1978). The resting membrane potential and ATPase activity of airway smooth muscle was assessed 60 minutes after incubation in a normal oxygenated physiological salt solution (pH = 7.38 +/- 0.02) at each of the following temperatures: 21 degrees, 29 degrees, 37 degrees and 40 degrees C. The effect of ouabain (10(-5) M) and histamine (10(-3) M) on resting membrane potential of airway smooth muscle cells was also determined at each of these temperatures. It was found that: (1) resting membrane potential of airway smooth muscle cells from both bovine and guinea pigs, was directly proportional to the temperature; (2) the administration of ouabain reduced the dependency of resting membrane potential on the temperature of the experimental medium; (3) at lower temperatures (21 degrees C and 29 degrees C), histamine-induced a statistically significant (P less than 0.01) depolarization, and the contractile response of airway smooth muscle was also significantly (P less than 0.01) potentiated; (4) a decrease in the temperature (29 degrees C) significantly (P less than 0.001) decreased (Na+ + K+)-ATPase activity of airway smooth muscle as measured by potassium-induced relaxation. It is concluded that a change in temperature has a direct influence on airway smooth muscle cells, affecting resting membrane potential, (Na+ + K+)-ATPase activity of airway smooth muscle cells, and the contractile response of these cells to histamine.