Abstract
Pathological studies suggest that cisplatin injures different portions of the nephron to different extents. To investigate this issue further, we examined the cytotoxicity and uptake of cisplatin in cell lines derived from S1 and S3 proximal tubule and distal convoluted tubule segments isolated from a mouse carrying the SV40 large T-antigen transgene. S1 cells displayed the highest sensitivity to cisplatin cytotoxicity, followed by S3 and distal convoluted tubule (DCT) cells. These differences in cytotoxicity did not correlate with differences in cisplatin uptake. Cytotoxic concentrations of cisplatin triggered apoptosis in all three cell lines. Although BAX and BCL-2 expression was similar among the three cell lines, the expression of the anti-apoptotic protein, BCL-X(L), was significantly lower in S1 cells than in S3 and DCT cells, and this may have contributed to the heightened sensitivity of S1 cells. Cisplatin transport characteristics demonstrated a saturable component of cisplatin uptake and differences in apparent K(M) and Vmax values among the three cell lines. The three cell lines were 43- to 176-fold more sensitive to cisplatin than to carboplatin. This distinction between the two drugs could not be fully explained by differences in the uptake rates of carboplatin and cisplatin. We conclude that cells from different portions of the nephron display different sensitivities to cisplatin, different transport characteristics for cisplatin and different levels of expression of BCL-X(L). In addition, the relative resistance of renal cells to carboplatin vs cisplatin is mostly due to the differential effects that follow internalization.