The chromatographic quantitation of 8-oxoguanine adducts in DNA is wid
espread in the literature, although results obtained by HPLC of 8-oxod
eoxyguanosine do not always agree with levels determined by GC-MS. To
help explain this discrepancy, here we describe a novel procedure for
the analysis of 8-oxoguanine adducts in DNA. Although it proved diffic
ult to directly quantitate 8-oxoguanine in the presence of high levels
of endogenous guanine using conventional reversed-phase HPLC, a simpl
e preincubation of DNA acid hydrolysates with guanase allowed such ana
lyses. The assay relied on our observation that 8-oxoguanine was not a
substrate for guanase, and on sensitive electrochemical detection. Th
e limit of detection for 8-oxoguanine was 5 nM or 250 fmol on column.
Using this procedure, the background level of 8-oxoguanine in commerci
ally available calf thymus DNA was 0.4 nmol/mg DNA or 3.2 mol/10(5) mo
l guanine.