The effect of alteration in temperature on contractile responses in human airways in vitro

We studied the effect of alteration in temperature on the contractile responses of human airway tissue in vitro. Responses to histamine, carbachol and potassium chloride were studied in two successive cumulative concentration response curves (CCRC) in each tissue in which the first CCRC was carried out at 37 degrees C and the second CCRC at either 20 or 37 degrees C. In the second histamine CCRC both at 37 and 20 degrees C the efficacy, i.e. the maximal response (Tmax) was reduced and at 20 degrees C the potency was reduced, i.e. the concentration required to produce half the maximum response (EC50) was increased. Potassium chloride Tmax was potentiated in the second CCRC at 37 degrees C but not at 20 degrees C. Reduction in temperature potentiated carbachol-induced contractile responses, i.e. the Tmax was significantly increased. Cooling produced a drop in baseline tension whereas warming the tissues or the addition of ouabain, 5 X 10(-5) M, to the bath produced a rise in baseline tension. It is concluded that contractile responses of human airway smooth muscle to carbachol but not histamine or potassium chloride are potentiated by cooling.