Comparison of effects of low temperature and metabolic inhibition on high-K induced contracture of vas deferens.

The effects of temperature on high-K induced contracture of guinea-pig vas deferens were studied and compared with those of metabolic inhibitions. The rate of rise and fall of the phasic contraction decreased with the decrease in temperature. At 5 degrees C, the time to peak tension and half relaxation time increased to 25 times and to 38 times of those observed at 35 degrees C, respectively. The height of the phasic contraction increased by lowering of the temperature. The height of the tonic contraction also increased by lowering the temperature down to 15 degrees C but then decreased. Glucose removal and anoxia showed no effect on the phasic contraction, whereas the tonic contraction was abolished by these treatments. Metabolic inhibitors such as DNP, NaN3 or KCN, caused the depression of both the phasic and tonic contractions, being more effective on the tonic contraction. The tonic contraction was abolished before the phasic contraction was depressed by 50%. The time to peak tension and half relaxation time were not affected by metabolic inhibitions. These results suggest that low temperature causes the reduction in the rate of contractile reaction of muscle protein and in the rate of Ca accumulation and/or of Ca extrusion. Metabolic inhibition, on the other hand, caused reduction in the energy supply for the contraction and brought about depression of the contraction.