Effect of lighium substitution for sodium on oxygen consumption of guinea pig taenia coli in high K medium.

It was reported that high potassium solution (isotonic, 40 mm) induced a tension development in guinea pig taenia coli accompanied by an increase in oxygen consumption (1). Intracellular Ca space increased in high K medium as well as cellular Ca fraction which did not exchange within 4 minutes. The latter is referred to "tightly bound fraction (TBF)" (2). By addition of ouabain (2.5 X 10-'m) to high K medium the increased oxygen consumption was maintained, although the developed tension was almost abolished, and both changes were dependent on external calcium (3). Moreover, the elevated intracellular Ca space was maintained by addition of ouabain, while the increased TBF returned to the control level in the high K medium (2). When lithium was substituted for sodium at a level above 50 mm in high K (hypertonic, 40 mm) me dium, the developed tension of the muscle gradually decreased to the original level (4, 5). In the present