Direct amphotericin B-mediated tubular toxicity: assessments of selected cytoprotective agents.

Amphotericin B (AB) may induce acute renal failure by vasoconstrictive and tubulo-toxic effects. Although mannitol, Ca2+ channel blockers, and lipid-based AB preparations have been suggested to mitigate in vivo AB nephrotoxicity, whether they confer direct tubular cytoprotection has not been defined. Therefore, this study assessed the impact of mannitol, verapamil/extracellular Ca2+, and cholesteryl sulfate (CS) AB binding on AB cytotoxicity, employing an isolated rat proximal tubular segment (PTS) preparation. After 30 to 60 minutes of incubation, 0.2 mg/ml of AB (Fungizone) caused marked toxicity, as assessed by LDH release (29 to 44%) and ATP depletion (greater than 90%). Approximately 40% of the LDH release could be attributed to deoxycholate, the standard AB (Fungizone) solubilizing agent. Both 100 mM mannitol and 100 mM glucose decreased AB-mediated LDH release, despite having a quantitatively trivial impact on ATP concentrations (increments of less than or equal to 1% at normal values). Dimethylthiourea (25 mM; equipotent to 100 mM mannitol/glucose as a hydroxyl radical scavenger) did not decrease LDH release. Neither verapamil addition (100 microM) nor Ca2+ removal from the PTS buffer had a protective effect. CS binding completely eliminated AB's toxicity (no LDH or ATP losses). The effect of AB and CS-AB on concomitant O2 deprivation/reoxygenation (30 min/15 min) PTS injury was also assessed. AB and hypoxia/reoxygenation caused additive, not synergistic, LDH release whereas CS-AB had no adverse effect.(ABSTRACT TRUNCATED AT 250 WORDS)