oligomycins and Ascites

The effect of the oxygen concentration on the rate of oxygen consumption by 786 and TA3 ascites tumor cell lines has been determined under steady-flow conditions with a membraneless fast-responding O2 electrode and using ascorbate and N,N,N',N'-tetramethyl-p-phenylenediamine as electron donors. The reaction was initiated by rapid injection of O2 into anaerobically incubated test system. The time-dependence of the intact cell respiration showed three distinct phases; an early very fast but short duration phase, a subsequent slow phase that prevailed for most of the reaction period and a third phase which preceded the reestablishment of anaerobiosis. Kinetic analysis of the reaction indicated a linkage between the catalytic efficiency and the transmembrane electrochemical potential. The rates of O2 uptake, obtained in the presence of both protonophores and ionophores, were monotonic and pseudo-first order over 90% of the course of O2 consumption. Extrapolation of the observed rates to zero time, at which zero delta mu H+ and thus constant flow prevails, was used to calculate the oxygen concentration for the half-maximal respiratory rate, which was found to be in the range 1.55-2.10 microM O2. No noticeable variation in the value of this kinetic parameter was found between the two cell lines used. Possible reasons for discrepancies in published reports on the oxygen dependence of the cytochrome c oxidase activity in various mitochondrial and reconstituted systems are discussed.

Topics: Animals; Ascites; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Cytochrome a Group; Cytochrome c Group; Cytochromes; Electron Transport Complex IV; Kinetics; Male; Mice; Mitochondria; Oligomycins; Oxidation-Reduction; Oxidative Phosphorylation; Oxygen Consumption; Tumor Cells, Cultured; Valinomycin

Several agents known to interact with the (Na+ + K+)-pump were tested for their effects on the components of steady-state K+ flux in ascites cells. 86Rb+ was used as a tracer for K+, and influx was differentiated into a ouabain-inhibitable "pump" component, a Cl--dependent and furosemide-sensitive "exchange" component, and a residual "leak" flux. All agents tested (ouabain, quercetin, oligomycin, phosphate) affected both the "pump" flux and the Cl--linked flux. These findings suggest a linkage between the activity of the Na/K ATPase and the Cl--dependent K+ exchange flux. In the discussion we point out that the mechanism of this linkage could be direct; e.g., Cl--dependent exchange may represent a mode of operation of the Na/K ATPase. However, data from this and other systems tend to suggest an indirect linkage between the Na+ pump and a KCl symporter, perhaps via a change in the level of intracellular ATP.

Topics: Animals; Ascites; Biological Transport, Active; Chlorides; Flavonoids; Mice; Neoplasms, Experimental; Oligomycins; Ouabain; Phosphates; Potassium; Quercetin; Sodium; Sodium-Potassium-Exchanging ATPase

Topics: Anti-Bacterial Agents; Antimetabolites; Ascites; Carcinoma, Hepatocellular; Cell Respiration; Dinitrophenols; Glucose; Liver Neoplasms; Metabolism; Neoplasms; Neoplasms, Experimental; Oligomycins; Pharmacology; Research