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Journal of Experimental Biology 56,551-563 (1972)
Published by Company of Biologists 1972

Ionic Distribution in Amoeba Proteus

ROBERT D. PRUSCH 1 and PHILIP B. DUNHAM 2

1 Department of Zoology, Syracuse University, Syracuse, New York, Division of Biological and Medical Sciences, Brown University, Providence, Rhode Island 02912.
2 Department of Zoology, Syracuse University Syracuse, New York

1. The intracellular concentrations of K, Na, Ca and Cl in Amoeba proteus are 24.83, 1 .08, 2.93 and 9.73 mM/kg cells respectively.

2. Intracellular Na is always slightly higher than that of the external medium when external Ca is low.

3. Addition of Ca to the medium reduces the intracellular concentration of Na by decreasing the permeability of the plasmalemma to Na.

4. The membrane potential of Amoeba proteus in Prescott-James medium is -89.5 mV and is sensitive to changes in both external K and external Na when external Ca is low.

5. Intracellular Na and K are both sensitive to the addition of CN to the external medium.

6. Both Na and K are actively transported in the amoeba; K is actively accumulated from the external medium and Na is actively expelled from the cell.

7. It has been suggested that the effects of Ca on Amoeba proteus, i.e. reduction of PNa, reduced internal concentration of Na, reduced unidirectional Na and K influxes, and increased membrane resistance are due to Ca binding to the plasmalemma.

Submitted on October 18, 1971




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R. Prusch
Endocytotic sucrose uptake in Amoeba proteus induced with the calcium ionophore A23187
Science, August 8, 1980; 209(4457): 691 - 692.
[Abstract] [PDF]


© The Company of Biologists Ltd 1972