Gentamicin uptake by renal tubule brush border membrane vesicles

The uptake of [³H]gentamicin by isolated rabbit renal proximal tubule brush border membrane vesicles was studied. Uptake was biphasic, with an initial rapid uptake followed by a prolonged slower phase. Approximately half of the total uptake respresented binding; the other half represented transport into an intravesicular space. Scatchard analysis indicated the presence of two binding sites, differing in affinity (8 x 10³ and 0.9 x 10³ M^-1) and number of sites per milligrams of protein (1.2 and 3.7 nmol/mg of membrane protein, respectively.) [³H] Gentamicin uptake was not affected by a Na⁺ electrochemical gradient, a valinomycin-generated (inside negative) K⁺ diffusion potential or the presence of phlorizin and D-or L-glucose. These findings indicate that the mechanism of uptake of the aminoglycoside was distinct from those of sugar and amino acids. Uptake of [³H]gentamicin was inhibited and reversed by the unlabeled aminoglycoside and by spermine. Spermine, on a molar basis, was as effective as gentamicin. These results suggest that gentamicin and spermine may have a common polyamine transport system and demonstrate the feasilibity of further investigations to prevent aminoglycoside accumulation and possibly subsequent nephrotoxicity.