The effect of Ammonium on the potassium content of unstriated muscle and its relation to the contraction produced on withdrawal of chemical substances from around the muscle

Summary

• (1) In frog stomach muscle, ammonium enters the cells and replaces potassium; this is associated with the ammonium withdrawal contraction having the properties of the A.C. contraction.

• (2) In dog muscle there is no significant difference between the potassium contents of muscles soaked in normal saline, and in ammonium-rich saline respectively; with this is probably associated the absence in dog muscle of the ammonium withdrawal contraction having the properties of the A.C. contraction.

• (3) Ammonium causes greater replacement of potassium than the tetra-ammonium salts; with this is probably associated the fact that the latter do not produce a contraction on withdrawal, similar to that of ammonium in frog muscle. Withdrawal of the latter salt produces a tonic contraction similar to that produced by withdrawal of ammonium in dog muscle.

• (4) There is greater loss of potassium produced by ammonium in alkaline than in acid solutions; but there is greater loss of potassium in a potassium-free saline in acid solutions. As the ammonium withdrawl contraction in frog muscle is more marked in acid than in alkaline solutions, it suggests that the contraction is due to the outward passage of the ammonium ion.

• (5) Slow relaxation of a contraction produced by a chemical substance may be due to tonic contraction on withdrawal of the substance or to persistence of the previous contraction, probably due to increase in viscosity of the muscle.