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The effect of glucose on chloride uptake by Chlorella: I. General characteristics of chloride transport

R. Doblinger and H.W. Tromballa
Planta
Vol. 156, No. 1 (1982), pp. 10-15
Published by: Springer
Stable URL: http://www.jstor.org/stable/23375779
Page Count: 6
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The effect of glucose on chloride uptake by Chlorella: I. General characteristics of chloride transport
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Abstract

Active Cl- uptake by Chlorella fusca was examined by using 36Cl as a label. Under light/air conditions chloride influx from a 2.4·10-5 M solution was 4.0 ± 0.04 nmol m-2 s-1. After 70 ± 10 min a stationary 380 ± 40 fold accumulation was reached. In dark/air and dark/argon influx and accumulation were reduced to 25 ± 6%, respectively, 5 ± 1.5% of the light/air control. Cl- uptake had a broad optimum around pH 7 and showed saturation kinetics with a KM of 1.25·10-5 M and a vmax of 7.0 nmol m-2 s-1 in light/air. Br- inhibited Cl- uptake strongly, J-, $\mathrm{C}\mathrm{l}{\mathrm{O}}_{4}^{-}$, $\mathrm{S}{\mathrm{O}}_{4}^{2-}$, and $\mathrm{N}{\mathrm{O}}_{3}^{-}$ had no inhibitory effect. Inhibitor studies with carbonyl cyanide m-chlorophenylhydrazone and N,N′-dicyclohexylcarbodiimide resulted in a good correlation between Cl- uptake and ATP level. 3-(3,4-Dichlorophenyl)-1,1-dimethylurea and darkness reduced transport activity without affecting the ATP level. The magnitudes of the pH gradient and the membrane potential across the cell membrane were determined and/or estimated under different conditions. It could be shown that in Chlorella Cl- transport cannot proceed via secondary active H+/Cl- cotransport. In addition, 2H+/Cl- cotransport seems unlikely for energetic reasons. On the basis of the results of this and the following study, a primary active ATP-driven Cl-/OH- exchange pump is proposed.

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