Respiratory Response of Acer pseudoplatanus Cells to Pyruvate and 2,4-Dinitrophenol

The endogenous respiration rate of unstarved cultured cells of Acer pseudoplatanus L. is markedly stimulated by 2,4-dinitrophenol. Pyruvate is also stimulatory but to a lesser degree than dinitrophenol. Exogenously supplied sugars cause no short-term stimulation. Pyruvate does not enhance the elevated rate of O2 uptake in the presence of dinitrophenol but does cause additional CO2 evolution. The endogenous concentration of pyruvate is elevated in the presence of dinitrophenol. These observations suggest that the rate of O2 uptake by the unstarved intact cells is limited by the rate of glycolysis and that rate of glycolysis is regulated by the intracellular concentration of adenine nucleotides or inorganic phosphate. Dinitrophenol stimulation of endogenous respiration is due in part to an indirect acceleration of glycolysis but also to a more direct facilitation of oxidation in the presence of excess mitochondrial substrate.