Excretion kinetics of the DNA adducts of cis-diamminedichloroplatinum(II) formed in vitro in rat urine.

The main adduct of cis-diamminedichloroplatinum(II) (cis-Pt) with DNA, cis-[Pt(NH3)2(dGpdG)], was administered i.p. to rats. Urine was collected daily for 4 days. The adduct was purified by a weak cation exchanger and quantitated by HPLC with UV detection. The recovery of the adduct was 30.0 +/- 7.0% (mean +/- SEM). The main reason for the low recovery was the chemical instability of cis-[Pt(NH3)2 (dGpdG)] in urine as shown in an in vitro incubation. Adjusted for this instability the recovery in urine was greater than 70% of the dose. When cis-Pt-DNA (the molar ratio of cis-Pt to nucleotide = 1:50) was administered i.p. to rats only 1.25 +/- 0.23% of platinum was excreted in urine in the form of cis-[Pt(NH3)2(dGpdG)] and cis-[Pt(NH3)2(dApdG)] during the first 4 days. If the removal of the cis-Pt-DNA adducts from human tissues is to be followed, their possible slow excretion and chemical instability in urine needs to be considered.