title: Determination of the rate of rapid pH equilibration across isolated sarcoplasmic reticulum membranes.
abstract: The rate of the transmembrane pH equilibration in the isolated vesicles of sarcoplasmic reticulum of skeletal muscle after extravesicular pH jump was determined for the first time. A highly water-soluble pH sensitive fluorescent dye, 8-hydroxy-1,3,6-pyrenetrisulphonic acid (pyranine), was used as intravesicular pH indicator in the stopped-flow fluorophotometry. The pH of the medium was controlled with 20 mM HEPES-K or PIPES-K. The fluorescence intensity changed monophasically as much as expected from its pH dependency for imposed delta pH. The half time for initial pH of 7.53 or 6.83 was about 6 msec. The H+/OH- permeability was 11 cm/sec. The results suggested that each vesicle contained large numbers of H+/OH- channels.
mesh_terms: D000818:Animals; D001190:Arylsulfonates; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D010539:Permeability; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D001190:Arylsulfonates; D005456:Fluorescent Dyes; C005047:pyranine