ascorbic-acid and 2-aminoisobutyric-acid

Topics: Adult; Aminoisobutyric Acids; Ascorbic Acid; Biological Transport, Active; Coronary Disease; Female; Genetic Variation; Hartnup Disease; Humans; Male; Nutritional Physiological Phenomena; Phenotype

ATP synthesis in ADP + P(i)-loaded membrane vesicles of the facultative alkaliphile Bacillus firmus OF4 at an external pH of 10.5 did not depend upon the presence of cell wall polymers, e.g. as a proton barrier or sequestration device. Upon energization with ascorbate plus phenazine methosulfate, vesicles at pH(out) = 7.5 generated an electrochemical proton gradient (delta p) of -160 mV, acid and positive out, whereas at pH(out) = 10.5, the delta p was -40 mV, alkaline and positive out. Nonetheless, ATP synthesis was more rapid at the more alkaline pH value, especially in the presence of 200 mM K2SO4, which markedly lowered the surface potential. No synthesis was observed upon abolition of the delta p. Respiration-derived transmembrane potentials (delta psi) energized ATP synthesis much better than an equally large diffusion potential. The diffusion potential failed to energize ATP synthesis above pH 9.5. When delta p, all in the form of a delta psi, was titrated downward at either pH 7.8 or 9.5, ATP synthesis by the latter vesicles was much less adversely affected in the delta p range of -150 to -50 mV, supporting the existence of a sparing, non-chemiosmotic energy component at high pH.

Topics: Adenosine Diphosphate; Alkalies; Aminoisobutyric Acids; Ascorbic Acid; Bacillus; Buffers; Cell Membrane; Membrane Potentials; Models, Biological; Oxidative Phosphorylation; Phosphates; Potassium; Protons; Salts

1. Ascorbic acid, diamide and N-ethylmaleimide inhibit Na+ + K+-ATPase activity in toad corneal epithelium. 2. Ascorbic acid, diamide and N-ethylmaleimide increase alpha-aminoisobutyric acid accumulation in this tissue. 3. The effects of these compounds on corneal amino acid and ion transport are not mediated through alterations in Na+ + K+-ATPase activity.

Topics: Aminoisobutyric Acids; Animals; Ascorbic Acid; Biological Transport; Bufo marinus; Cornea; Dehydroascorbic Acid; Diamide; Epithelium; Ethylmaleimide; Glutathione; Glutathione Disulfide; In Vitro Techniques; Sodium-Potassium-Exchanging ATPase

Topics: Acetylcholinesterase; Aminoisobutyric Acids; Animals; Ascorbic Acid; Catecholamines; Cattle; Cells, Cultured; Chromaffin System

Primary cultures of bovine adrenomedullary cells actively take up ascorbic acid and alpha-aminoisobutyric acid (AIB). Following a brief incubation with L-[14C] ascorbic acid and alpha-[methyl-3H]aminoisobutyric acid, cells stimulated with the nicotinic agonist 1,1-dimethyl-4-phenylpiperazinium iodide or by membrane depolarization with high [K+] or veratridine released newly acquired ascorbic acid (NA-ascorbate) and AIB. NA-ascorbate and endogenous catecholamines are differentially released under a variety of conditions suggesting that release of both substances cannot originate from the same subcellular compartment. In contrast, the release profile for NA-ascorbate and AIB, a putative cytosolic marker, suggest that both of these molecules are released from a cytosolic compartment. Cells permeabilized with the detergent digitonin release catecholamines only in the presence of external Ca2+, whereas release of NA-ascorbate and AIB is Ca2+-independent and time- and detergent concentration-dependent. If the osmolality of the external medium is made either hyper- or hypoosmotic, 1,1-dimethyl-4-phenylpiperazinium iodide-induced release of endogenous catecholamines is inhibited. Release of NA-ascorbate and AIB, however, is progressively inhibited with increasing osmolality and enhanced with decreasing osmolality. Furthermore, differential release of NA-ascorbate and AIB as compared to soluble acetylcholinesterase, which is apparently released form the cisternae of the endoplasmic reticulum, was also observed. To determine the mechanism by which NA-ascorbate and AIB are released from the cell, the requirements for their maximal release were investigated. Release of NA-ascorbate and AIB was sensitive to inhibitors (both metabolic and transport) and to changes in the external ionic environment. The metabolic inhibitors carbonyl cyanide p-trifluoromethoxyphenylhydrazone and KCN (when incubated simultaneously with 2-deoxyglucose) inhibited NA-ascorbate and AIB release by greater than 75%. In contrast, the Na+-K+-ATPase inhibitor ouabain enhanced veratridine-induced release of NA-ascorbate by nearly 100% and had an even greater effect on AIB release. Changes in the external ionic environment (i.e. Na+ and/or Cl- substitution) inhibited both NA-ascorbate and AIB release to varying degrees. Substitution of Cl- by various anions inhibited NA-ascorbate and AIB release to a much greater degree than endogenous catecholamine release. Complete substitution of NaCl with sucros

Topics: Acetylcholinesterase; Adrenal Medulla; Aminoisobutyric Acids; Animals; Ascorbic Acid; Biological Transport; Catecholamines; Cattle; Cell Membrane Permeability; Cells, Cultured; Cytosol; Digitonin; Kinetics

The potential of ascorbic acid acting against the toxic effects of active oxygen species on the lens has been studied. The active species of oxygen were generated by the action of xanthine oxidase on xanthine. Rat lenses incubated in medium containing xanthine and xanthine oxidase were physiologically damaged, as evidenced by the decrease in the ability of the tissue to accumulate rubidium or alpha-aminoisobutyric acid against a concentration gradient. The pressure of ascorbate in the medium protected against the tissue damage. One of the functions of high ascorbate in the aqueous humor of many primates including human beings may, therefore, be to protect the lens and other surrounding tissues against the toxic effects of active oxygen derivatives produced in situ under ambient, as well as under photochemical, conditions.

Topics: Aminoisobutyric Acids; Animals; Ascorbic Acid; Hydrogen Peroxide; In Vitro Techniques; Lens, Crystalline; Rats; Rats, Inbred Strains; Rubidium; Time Factors; Xanthine; Xanthine Oxidase; Xanthines