Quantitation of hydrogen ion and potential gradients in gastric plasma membrane vesicles

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Abstract
The ATP-dependent uptake of H+ by hog gastric parietal cell vesicles was quantitated by using the pH indicator dyes bromcresol green and malachite green, the weak bases, aminopyrine and 9-aminoacridine and the pH electrode. A K+-dependent H+ uptake was found, with a significant difference between the quantity of H+ disappearing from the medium (.DELTA.Ho) and the quantity appearing inside the vesicle (.DELTA.Hi). 9-Aminoacridine gave a lower value for the .DELTA.Hi than any of the other probes. Probes of potential such as diethyloxadicarbocyanine or oxonol dyes showed that only secondary diffusion potentials occurred during H+ uptake and that the cationic dyes in the presence of protonophores could also be used to quantitate H+ uptake. The potential in the presence of protonophore indicated a .DELTA.Hi greater than that found with the other probes. Binding sites for acridine orange were generated either by ATP or an artificial pH gradient and corresponded to the .DELTA.Hi indicated by aminopyrine. SCN- (30 mM) only partially inhibited the H+ gradient. Coupled with this, the failure to detect the physiological .DELTA.pH [change in pH] of 6.6 indicated that these vesicles may be an incomplete model of gastric acid secretion.