Carcinogenesis
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Concurrent administration of para-aminobenzoic acid (PABA) reduced the toxicity of cis-diamminedichloroplatinum(II) (DDP) in a dose-related manner in rats. When administered i.p. simultaneously with 7.5 mg/kg DDP, PABA (100 mg/kg) significantly reduced plasma urea nitrogen (PUN) and plasma creatinine levels as well as DDP-induced weight loss. Increasing doses of PABA (25, 50 and 100 mg/kg) correlated with progressively better parameters of renal activity and body wt and with lower levels of platinum in plasma and tissues in rats killed 5 days after drug administration. ⋯ Analysis of tissue platinum content demonstrated significantly lower platinum levels both in kidneys (P < 0.05) and testes (P < 0.01) of mice receiving DDP and PABA in normal saline compared to those receiving only DDP in normal saline. PABA did not affect the in vivo and in vitro antitumor activity of DDP against P388 leukemia, and there was no significant PABA-induced modification in the concentration of platinum both in the tumor cells and in DNA samples isolated from P388 leukemic cells of DDP-treated mice. We conclude that PABA may be a promising compound for reducing DDP-toxic side effects, including nephrotoxicity, without compromising its antitumor activity.