Acridine orange transport in canine renal brush-border membrane vesicles

Acridine orange, a weak base, has been used to fluorimetrically measure pH changes in brush-border membrane vesicles (BBMV). Hitherto, its distribution across the plasma membrane had been believed to be solely due to ionic diffusion or nonmediated means. In a previous study, we first observed that acridine orange had an effect on the organic cation/H super(+) antiporter in BBMV. The purpose of this report is to clarify this interaction by examining the effect of acridine orange on the transport of N super(1)-methylnicotinamide (NMN), a prototypic organic cation, in canine renal BBMV. The results demonstrate that acridine orange was transported across the brush-border membrane via the organic cation transporter.