OBJECTIVETo study whether aristololactam I (AL-I) can enter renal proximal tubular epithelial cells and the situation of intracellular distribution and accumulation.

METHODCultured human renal proximal tubular epithelial cell line (HK-2) was used as the subject. Intracellular fluorescence from AL-I and its distribution are examined by fluorescence microscopy after a treatment with different concentration of AL-I, the intracellular accumulation of AL-I was also investigated by incubated cells in AL-I -free medium for 48 h after washing-out the media containing AL-I.

RESULTAfter treatment of AL-I (concentration from 5 microg x mL(-1) to 20 microg x mL(-1)), glaucous fluorescence could be observed inside renal proximal tubular epithelial cells at 0.5 h, and the fluorescence distributed only in cytoplasm while not be observed in nuclei. Moreover, the fluorescence of AL-I could be kept in cytoplasm for more than 48 h after washing out the media containing AL-I .

CONCLUSIONAL-I is able to enter renal proximal tubular epithelial cells in short time and accumulate in cytoplasm, but not enter nuclei. This property may contribute to the cytotoxic mechanism of renal injury induced by AL-I, which may partially explain the persistent renal toxicity of AAs and its metabolites in the development of aristolochic acid nephropathy.