A comparison of the effects of temperature and metabolic inhibition on the contraction of smooth muscle.

The effects of temperature and metabolic inhibitors on short tetanus contraction of vas deferens were studied. The contraction height increased by lowering temperature from 35 degrees C, and decreased with a decrease in temperature below 25 degrees C. The maximum speed of contraction and relaxation decreased by lowering the temperature, showing a transition of Q10 values at 25 degrees C. The Q10 value for the maximum speed of contraction was 1.7 between 35 to 25 degrees C, and 5.3 between 25 to 10 degrees C. The Q10 value for the maximum speed of relaxation was 1.9 between 35 and 25 degrees C, and 13.0 between 25 and 15 degrees C. The time to peak tension and to half relaxation increased by lowering temperature. The Q10 values also showed a transition at 25 degrees C. The Q10 value for the time to peak tension was -2.5 between 35 and 25 degrees C, and -5.0 between 25 to 5 degrees C. The Q10 value for the time to half maximum relaxation was -3.1 between 35 and 25 degrees C, and -5.7 between 25 and 5 degrees C. NaN3 and KCN and DNP inhibited the contraction. However, time to peak tension and half maximum relaxation time were not altered. Although the maximum speed of contraction and relaxation decreased, this was caused only by the reduction in peak tension. O2-free or glucose-free treatment caused only a slight decrease in peak tension. Neither time to peak tension nor half maximum relaxation time was altered. The differences between the effects of temperature and metabolic inhibition are discussed.