Ionic changes in unstriated muscle immersed in sodium-free solutions

Summary and Conclusions

1. Frog’s stomach muscle responds when immersed in hypotonic sucrose solution. The more thoroughly, sodium is eliminated from the external medium, the better it responds.

2. After the muscle has acclimatised to sucrose solution, re-immersion in solution of sodium chloride, or sodium chloride containing a little calcium or potassium abolishes the spontaneous contractions.

3. The sodium and potassium concentration in the muscle after immersion in sucrose for 4 hours becomes 0·0018 m.Eq. and 0·03 m.Eq. respectively per ml. of water in the muscle.

4. The mechanical response of the muscle in sucrose solution varies as the intracellular potassium.

5. These experiments suggest that intracellular potassium, and not extracellular sodium, that is mainly responsible for excitability of the muscle.