PURPOSE The specific activity of sodium-potassium-adenosine triphosphatase (Na-K-ATPase) in lens fiber cells is lower than the specific activity in lens epithelium. To test whether there is a reduction in the expression of Na-K-ATPase molecules in lens fibers, a Western blot technique was used. METHODS Membrane material was isolated from different regions of the rabbit lens. Na-K-ATPase (aden...

The phosphotransacetylase of Veillonella alcalescens catalyzes a reversible reaction with Michaelis-Menten kinetics for all substrates. The rate of the reverse reaction (the synthesis of acetyl coenzyme A from acetyl phosphate) was 6.5 times greater than the rate of the forward reaction (the synthesis of acetyl phosphate from acetyl coenzyme A). The apparent K(m) values determined for the forwa...

Solutions of adenosine triphosphate (ATP) were injected into the left coronary artery of isolated nonperfused dog hearts kept for 30 to 180 minutes at temperatures varying from 4 to 34°C. The amount of ATP administered varied from 0.5 to 7 /xmoles/g heart. The left ventricles of the ATP-treated hearts had a higher content of adenine nucleotides and of phosphocreatine than did the left ventricle...

In the course of studies on the acid-soluble phosphorus compounds of liver and kidney, it became evident that the fraction comprising the nucleotides represented a complex mixture (1). In an attempt to isolate the individual nucleotides, methods designed to minimize the breakdown of labile phosphorus compounds were employed. The isolation of adenylic acid and of a material representing a mixtur...

Acetokinase from Veillonella alcalescens catalyzes the virtually irreversible synthesis of adenosine triphosphate from acetyl phosphate and adenosine diphosphate. Kinetic analysis revealed that the enzyme was activated by acetyl phosphate and inhibited by adenosine triphosphate. Velocity curves obtained with increasing amounts of adenosine diphosphate were of the Michaelis-Menten type (rectangu...

It has been proposed that extracellular ATP inhibits synaptic release of glutamate from hippocampal CA1 synapses after its catabolism to adenosine. We investigated the possibility that at least part of this effect is mediated by ATP itself acting on P2Y receptors. ATP and various analogs decreased the amplitude and duration of glutamate-mediated excitatory postsynaptic potentials in all tested ...

A luminescent probe based on a europium complex is developed, which effectively distinguishes adenosine-5'-triphosphate (ATP) from adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in pure water at pH 6.8. With a longer lifetime (in ms range), the probe is prospectively applied to biological systems to monitor ATP levels by completely removing the background fluorescence of other mo...

The cardiotoxic effects of Adriamycin (ADM) were studied utilizing mammalian myocardial cells in culture as a model system. ADM inhibited cell growth and the rhythmic contractions characteristic of these cells. Because a possible involvement of energy metabolism in the action of ADM was suggested previously, the adenylate energy charge and phosphorylcreatine mol fraction were determined in the ...

Adenosine and the adenine nucleotides caused a greater relaxation of strips of canine saphenous vein and tibial artery when they had been contracted by nerve stimulation than by exogenous norepinephrine. An infusion of adenosine into the dogs' lateral saphenous vein, perfused at constant flow, caused a greater relaxation of this vein when constricted by electrical stimulation of the lumbar symp...

ATP and several congeners were applied to locus coeruleus neurons in slices cut from rat pons. Whole-cell recording of membrane current showed that ATP caused an inward current at -60 mV. Effective concentrations (applied by superfusion) were 3-300 microM, and the peak current was about 150 pA at -60 mV. 2-Methylthioadenosine 5'-triphosphate was slightly more potent than ATP, adenosine 5'-dipho...