H Permeability of apical membrane vesicles from the upper gastrointestinal tract

Abstract

Apical membrane vesicles were isolated from the rabbit brush border (dBBMV) and histamine stimulated oxyntic cells (SAV). Proton permeation was monitored from acridine orange fluorescence quenching,+following imposition of a transmembrane H gradient. The process followed first order kinetics, with rate constants o 4. 520.22 (n=20) and 2.15k0.14 (n= 14) x lo-?s-f (temp=20°C). for dBBMV and SAV respectively Fluorescence anisotropy (r) of diphenylhexatriene indicated the fluidity of the lipid bilayer (expressed as (r Me/ r)-1, r = limiting anisotropy (0.362)). dBB and &V gave values of 0.488+0.013 (n=7) and 0.66* (n==4) respectively. Increases in temperature, and treatment with a sqries of alcohols, increased(rdr)-1, and H permeation in the case of SAV than dBBMV. Arrhenius plots of the two parameters demonstrated discontinuities at 30°C in the case of dBBMV, but not SAV.