Autoradiographic study of tobramycin uptake by proximal and distal tubules of normal and pyelonephritic rats.

Multiple factors may modify the pharmacokinetics of aminoglycosides and affect their nephrotoxic potential. In the present study, the influence of Escherichia coli pyelonephritis on the renal handling of [3H]tobramycin was investigated. The accumulation of [3H]tobramycin in proximal and distal tubules in both normal and infected rats was compared. Following induction of pyelonephritis, disturbed intrarenal localization of the drug was noted. Grain counts were affected in both proximal and distal tubules. Decreased labeling was observed at all time intervals in the proximal tubules. Electron microscopy showed that radioactivity was associated mostly with lysosomes in both normal and infected rats 1 and 24 h following the injection of the drug. We could detect significantly higher amounts of drug in the distal tubules of the pyelonephritic kidney than the normal levels at 10 min and 24 h postinjection. The drug did not seem to be associated with any particular organelle and was evenly distributed within the distal tubular cells. The present study shows that the transport of tobramycin within the infected nephron is disturbed. These data might shed some light on the influence of infection on the intrarenal pharmacology of aminoglycosides.