Total extraction of aminoglycosides from guinea pig and bullfrog tissues with sodium hydroxide or trichloroacetic acid

In most experiments when aminoglycoside antibiotic (AG) tissue levels are measured, the AG is extracted into buffered media. The data from this study reveal that buffer extraction results in only partial recovery of AG from tissues and that total recovery can be obtained after NaOH or trichloroacetic acid treatment. Tissues studied here included the whole bullfrog and guinea pig kidney and cochlear tissues after in vivo drug treatment. The AGs used were kanamycin, tobramycin, and gentamicin. Drug concentrations were determined by enzymatic assay and, in the case of tobramycin, also 3H-labeled radioactivity. Only a fraction of total concentration of AG in tissue was released into the supernatants of tissue homogenates. However, the remainder was recovered after NaOH solubilization of the residual pellet. Also, it was found that the G released from the pellet by NaOH was associated with protein. By contrast, trichloroacetic acid precipitation of tissue protein immediately released the drug into the supernatant.