[Anion regulation of active transport of protons across the membrane of the synaptic vesicles of the brain].
The dependence of active transport of H+ on the presence of anions in synaptic vesicle membranes from rat brain was studied. The H+ transport was measured by monitoring the acidification of the vesicles with a permeant weak base-acridine orange. The fluorescence changes in the latter were proportional to the magnitude of artificially imposed pH gradients (delta pH). The ATP-dependent generation of delta pH was completely dependent on the presence of a permeant anion, was maximal at 150 mM Cl- and was inhibited, when the medium osmolarity was further increased by sucrose or KCl. At 150 mM only Br-, similar to Cl-, behaved as permeant anions, whereas I- was effective only at low (5-20 mM) concentrations. The anions--SCN-, ClO4-, HSO3- and I-(10-20 mM) as well as 4-acetamido-4'-isothiocyanatostilbene-2.2'-disulfonate (K0.5 = 14 microM) blocked the ATP-dependent generation of delta pH observed in the presence of Cl-, while other anions tested (F-, phosphate, bicarbonate, some organic anions) were virtually without effect and did not support the H+ transport. The dependence of the rate and extent of H+ accumulation on Cl- concentration was sigmoidal with a Hill coefficient of 2.8 and a Km value of 85-90 mM. The effects of anions point to the presence in the membrane of synaptic vesicles of an anion (chloride) channel whose conductance can regulate the H+ transport by switching it from an electrogenic to an electroneutral (coupled entry of H+ and Cl-) mode of operation.
D000818:Animals; D000838:Anions / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects; D007700:Kinetics; D010539:Permeability; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D011522:Protons; D051381:Rats; D013570:Synaptic Membranes / Q000378:metabolism*; D013572:Synaptic Vesicles / Q000378:metabolism*
D000838:Anions; D002712:Chlorides; D007473:Ion Channels; D011522:Protons; D006180:Proton-Translocating ATPases
Anionnaia reguliatsiia aktivnogo transporta protonov cherez membranu sinapticheskikh puzyr'kov mozga.