The effects of valinomycin on respiration and volume changes in plant mitochondria

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The effects of valinomycin on the respiration and volume changes have been studied with isolated mitochondria from bean hypocotyl (Phaseolus vulgaris L.) and cauliflower bud (Brassica oleracea L.). In the presence of 10 mM K salts of chloride, acetate, phosphate, and sulfate respiration is stimulated by valinomycin concomitant with osmotic swelling. When swelling declines respiration with organic acid substrates also declines. In the presence of the K salts of acetate and PO_4 but not Cl^- the termination of respiration leads to contraction. The contraction in K-PO_4 is inhibited by addition to the external medium of between 65 to 100 mM K-PO_4. The results are interpreted to suggest that valinomycin in the presence of KCl facilitated the movement of K down an electrical gradient, with the Cl anion following and osmotic swelling resulting. However, in a medium containing acetate or PO_4 the anions are actively transported against an electrical gradient at the expense of metabolic energy. Valinomycin facilitates the influx of K^+ with the actively transported anion and swelling follows. When respiration terminates the actively transported anions move passively back down their electrochemical gradient and osmotic contraction follows.
日本植物生理学会の論文