TRANSPORT OF GENTAMICIN IN RAT PROXIMAL TUBULE

  • 1 January 1983
    • journal article
    • research article
    • Vol. 48  (2) , 212-223
Abstract
The intrarenal distribution of 3H-gentamicin (GM) [an antibiotic] was determined in rat by combined immunofluorescence and section freeze-dry autoradiography, techniques that permit subcellular localization before and after diffusional redistribution. Tissue from these kidneys was also examined by EM. After parenteral administration of 4-100 mg/kg, GM accumulates in S1 and S2 but not S3 segments of proximal tubules. Within 10 min, autoradiography demonstrates 3H-GM in the lumina of proximal and distal tubules; a subapical distribution consistent with pinocytotic uptake is prominent in many proximal cells. After 1 h, 3H-GM is diffusely distributed within the cytoplasm in section freeze-dry autoradiographs with minimal evidence of intracellular sequestration. At this time, 3H-GM is presumably within endocytotic vacuoles, and EM reveals only rare vacuoles containing single myeloid bodies. Subsequently, section freeze-dry autoradiography shows sequestration of the aminoglycoside, but this intracellular localization is lost during tissue processing for fluorescent microscopy up to 6 h after injection. At 6 h large cytoplasmic vacuoles containing multiple well-organized myelin figures first appear in S1 and S2 segments. By 48 h, 3H-GM is firmly bound in these vacuoles and is maintained in situ in both section freeze-dry autoradiographs and immunofluorescent preparations in association with increased numbers of vacuoles containing multiple myeloid bodies by EM. Evidently, diffusible 3H-GM within the cell is available to initiate nephrotoxicity 1-6 h after administration.

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