THE EFFECT OF SODIUM, POTASSIUM AND CALCIUM IONS ON CHANGES IN VOLUME OF AMOEBA PROTEUS

¹ From the Zoölogical Laboratory of the Johns Hopkins University

1. If amoebae are transferred from modified Ringer solution (0.002 M, pH 6.8) to distilled water or to phosphate buffer solution containing respectively sodium, potassium and calcium as the only metallic cation (0.002 M, pH 6.8), they increase in size in distilled water, decrease in size in the solution which contains potassium and remain nearly the same in size in the solution which contains sodium or calcium.

2. If they are transferred from modified Ringer solution (0.002 M, pH 6.8) to distilled water containing lactose (0.2 M) or to phosphate buffer solutions containing lactose (0.2 M) and respectively sodium, potassium and calcium as the only metallic cation, they decrease in volume in all the solutions but they decrease most rapidly in distilled water containing lactose, less rapidly in the solution containing sodium and lactose, still less rapidly in the solution containing potassium and lactose, and least rapidly in the solution containing calcium and lactose.

3. If they are transferred from modified Ringer solution (0.002 M, pH 6.8) to Ringer solution containing lactose (0.2 M) and left 30 minutes, they decrease greatly in volume. If they are then transferred respectively to distilled water and to phosphate buffer solutions, containing respectively sodium, potassium and calcium (0.002 M, pH 6.8), they increase in volume in all the solutions, but they increase most rapidly in distilled water, less rapidly in the solution containing sodium, still less rapidly in the solution containing potassium and least rapidly in the solution containing calcium.

4. These results show that under some conditions monovalent as well as divalent cations cause decrease in the rate at which water passed into and out of Amoeba proteus. This is probably largely due to their action on permeability to water.