Influence of organic acids on intracellular pH.
By use of double-barreled pH-sensitive microelectrodes, intracellular pH was measured in isolated sheep cardiac Purkinje strands. After equimolar substitution of 20 mmol/l Cl- by several organic anions at constant extracellular pH 6.8, the rate of induced intracellular acidification was measured. For many organic acids tested, a relation was found between the rate of intracellular acidification and the product of their dissociation constant (pK'a) and diisopropylether-to-water partition ratio (p'). L-Lactate and pyruvate, and also cyanoacetate and alpha-ketobutyrate, caused faster acidifications than anticipated from their pK'a and p'. The rate of intracellular acidification, induced by L-lactate and pyruvate, was markedly depressed in the presence of 4 mmol/l alpha-cyano-4-hydroxycinnamate, a known inhibitor of the carrier-mediated pyruvate transport. The drug also had an effect on the acidification produced by cyanoacetate, alpha-ketobutyrate, glycolate, alpha-hydroxybutyrate, and alpha-chloropropionate, but not on that produced by propionate and acetate. L-Lactate caused a faster acidification than D-lactate. Our results suggest the existence of a facilitated diffusion for L-lactate, pyruvate, and some other organic acids in sheep Purkinje cells.
D000818:Animals; D002264:Carboxylic Acids / Q000378:metabolism* / Q000494:pharmacology; D006329:Heart Conduction System / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007773:Lactates / Q000494:pharmacology; D019344:Lactic Acid; D008433:Mathematics; D008564:Membrane Potentials / Q000187:drug effects; D011690:Purkinje Fibers / Q000502:physiology*; D012756:Sheep; D013329:Structure-Activity Relationship
D002264:Carboxylic Acids; D007773:Lactates; D019344:Lactic Acid