Induction and intracellular localization of 90-kilodalton heat-shock protein in rat kidneys with acute gentamicin nephropathy.

BACKGROUND: We previously reported the induction of 73-kilodalton heat-shock protein (HSP73) in injured tubular epithelial cells in rat kidneys with gentamicin-induced acute renal failure. In the present study, we examined serial expression of 90-kilodalton heat-shock protein (HSP90), another major HSP, in this animal model. EXPERIMENTAL
DESIGN: Sprague-Dawley rats received gentamicin (80 mg/kg/day) for 14 days and developed acute proximal tubular injury. Serial immunohistochemical localization of HSP90 was observed at both light microscopic and electron microscopic levels, using a specific antibody against HSP90. In addition, serial renal extracts were analyzed by immunoblot.
RESULTS: On light microscopy, HSP90 was induced in injured proximal tubular epithelial cells and accumulated in fine granules 36 hours after the gentamicin exposure. The size and number of these granules gradually increased to Day 12 and decreased from Day 18, and the granules disappeared on Day 27. Electron microscopy showed the accumulation of HSP90 in the swollen lysosomes and the nucleoli of the injured proximal tubular epithelial cells. On serial immunoblot analysis of renal extracts, increased amounts of HSP90 were found in association with the induction of HSP90 in injured cells. Furthermore, on immunoblot of nuclear fractions from kidneys at Days 0 and 6, HSP90 was detected in the fraction at Day 6.
CONCLUSIONS: These results demonstrate that HSP90 is induced in the lysosomes and the nucleoli of damaged cells during the course of gentamicin-induced acute tubular injury. HSP90 may have roles in the disposition of degenerated proteins and in the new protein synthesis for the protection and repair of target cells from gentamicin nephrotoxicity.