A Quantitative Simulation Model for H+-Amino Acid Cotransport To Interpret the Effects of Amino Acids on Membrane Potential and Extracellular pH

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Abstract
The H+ cotransport of neutral and acidic amino acids induces transient depolarizations of oat coleoptile (Avena sativa L., var Victory) plasma membranes. The depolarizations, which are completed within 1 or 2 minutes, are followed by repolarizations that are nearly completed within another 2 or 3 minutes. Cysteine induced a two-phased alkalinization of the tissue free space during the electrical changes. The first phase was a rapid, linear increase in pH that coincided with the depolarization; the second phase was a slower, also linear, increase in pH that coincided with the repolarization. Reacidification did not occur until cysteine was withdrawn. Five other acidic, basic, and neutral amino acids also induced persistent alkalinization of the free space.