. Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954. Electrophysiology; Electrolytes; Electrolytes; Electrophysiology; Physiology, Comparative. ASER ROTHSTEIN 75 were not only taking up K+, but they were also exchanging cellular K+ for K*^ in the medium. The leakage of K+ associated with active metabolism has been investigated recently at very low K+ concentrations (47). Typical data are presented in figure 5. If cells are suspended in 3 X io~* m/1. KCl plus glucose, at pH
. Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954. Electrophysiology; Electrolytes; Electrolytes; Electrophysiology; Physiology, Comparative. ASER ROTHSTEIN 75 were not only taking up K+, but they were also exchanging cellular K+ for K*^ in the medium. The leakage of K+ associated with active metabolism has been investigated recently at very low K+ concentrations (47). Typical data are presented in figure 5. If cells are suspended in 3 X io~* m/1. KCl plus glucose, at pH , the K+ concentration drops rapidly to about 5 X io~* m/1. but no further. If the initial concentration is 5 X io~* m/1., then no changes in concentration occur. However, if the cells are suspended in distilled water, K+ leaks out of the cells rapidly until its concentration in the medium builds up to 5 X io~^ m/1. Thus at 5 X io~^ m/1. a steady state condition exists in which the rate of leakage and uptake are exactly equal. In the absence of substrate, there is no steady state condition, but K+ continues to leak out at a slow rate for long periods of time. Fig. 5. Gain or loss of K+ by media of different initial K""" con- centrations containing actively metabolizing yeast The kinetics of K+ leakage can be readily characterized if the K+ concentra- tion can be maintained at levels below the steady state concentration, 5 X lo"^ m/1. in this case. Ordinarily, it is difficult to study K+ leakage and uptake at low K+ concentrations because the cells establish the steady state in a few minutes. The problem has been resolved by passing the medium continuously through a column of packed cells at a rate such that the medium is in contact with the cells for only a short period of time. Samples of the medium are taken continuously by a standard fraction collector and analyzed for ionic content. By this technique K+ leakage or uptake can be studied in a syste
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