Ion permeability of rabbit intestinal brush border membrane vesicles

Abstract

The ion permeability of rabbit jejunal brush border membrane vesicles was studied by measuring unidirectional fluxes with radioactive tracers and bi-ionic diffusion potentials with the potential-sensitive fluorescent dye, diS-C3-(5). Tracer measurements provide estimates of the absolute magnitudes of permeability coefficients, while fluorescence measurements provide estimates of relative and absolute ion permeabilities. The magnitudes of the permeability coefficients for Na+, K+, Rb+, and Br- were approximately 5 nanoliters/(mg protein X sec) or 10(-5) cm/sec as determined by radioactive tracer measurements. The apparent selectivity sequence, relative to Na+, as determined by bi-ionic potential measurements was: F-, isethionate, gluconate, choline (less than 0.1) less than Na+(1.0) less than Cl-(1.5) = NO-3(1.5) less than Br-(2.3) less than K+(2.4) less than Rb+(2.5) less than Cs+(2.6) less than Li+(3.9) less than NH+4(12) less than I-(40). The origin of this selectivity sequence and its relationship to the ion permeability of the brush border membrane in the intact epithelium are discussed.

Fluorometric Assay of Potential Change ofBombyx moriMidgut Brush Border Membrane Induced byδ-Endotoxin fromBacillus thuringiensis

“…Gunther et at. 18) measured the permeability of rabbit intestinal BBMV to various ions by using of diS-C 3 -(5). The fluorescence of the dye also depended on the potential across BBMV isolated from Bombyx mori midgut (Fig.…”

Electrophysiology of succinate transport across rabbit renal brush border membranes.

“…An Aminco DW-2UV/VIS dual wave-length spectrometer was used to measure the difference in absorbance between 655 and 685 nm. The voltage response of the dye was calibrated by measuring K+ diffusion potentials in the presence of valinomycin, and bi-ionic diffusion potentials were recorded as described for intestinal brush border vesicles (Gunther, Schell & Wright, 1984). Vesicles (0 4 mg protein) were added to cuvettes containing 2-3 ml 100 mM-salt buffered to pH 7-5 with 10 mM-Tris/HEPES and made isotonic with the intravesicular solution using mannitol.…”

“…of the mean was less than 6 % of the mean. Relative permeability coefficients were calculated from the bi-ionic diffusion potentials, the ion gradients and the constant field equation (Gunther et al 1984). In these vesicles the relative permeabilities were Pgluconate 0-18 + 0-01 (n = 4); PNa 0-54 + 0-02 (n = 6), PK 1-00.…”

Effects of Amphotericin B on Renal Transport

“…The activity of membrane transport was observed using the potential sensitive dye 3,3-dipropylthiadicarbocyanine iodide [1]. Because Na + -dependent transport systems are electrogenic, their activity can be observed as changes in membrane potential, which, in turn, are proportional to the observed fluorescence response of the dye [2], In the absence of amphotericin B, the kinetics of N a+-dependent transport was observed and demonstra ted classical saturable response ( fig. 1, top curve).…”