Effect of anoxia on isotonic shortening induced by high-K medium in rat uterus.

The effect of anoxia on the shortening induced by high-K medium was investigated in isolated rat uterus. The shortening induced by high-K medium was maintained for 75 min or more under normoxia in the initial load (0.35 g). Under normoxia 1, 2, 2.5, and 3 g load to the uterus reduced the maximum shortening induced by high-K medium to 93, 65, 18 and 3%, respectively. Under anoxia the high-K-induced shortening in the initial load was not so affected and it was maintained at least for 60 min. However, against 0.7 and 1 g load to the uterus, the maximum shortening reduced greatly to 14 and 13% under anoxia. Effects of anoxia on the shortenings induced by high-K medium in guinea pigs taenia coli and longitudinal muscle from ileum were also studied. Our observations support the theory that the shortening of the light loaded muscle under anoxia is maintained by only a little force and the muscle may not be so dependent on metabolic energy.