8-hydroxyguanine and 2-nitropropane

A simple means of measuring of 8-hydroxyguanine (8-OHGua) levels in urine was developed. Rat and human urine samples were purified by means of strong cation exchange chromatography (Amberlite CG-120), followed by cellulose partition chromatography (Whatman CF-11). Thereafter, 8-OHGua was determined by means of high performance liquid chromatography (HPLC) using an electro-chemical detector. The level of 8-OHGua in rat urine increased by a factor of 2 to 4 after an intraperitoneal administration of 2-nitropropane (25 mg/kg), paraquat (11.3 mg/kg), or hydroquinone (11 mg/kg). On the other hand, the urine of smokers and persons exposed to air polluted with car exhaust also contained 1.9 and 3.8 fold more 8-OHGua, respectively, than that of control nonsmokers. These results indicated that the amount of 8-OHGua in urine is useful marker for monitoring the level of in vivo oxidative stress.

Topics: Adult; Air Pollution; Animals; Biomarkers; Chromatography; Free Radicals; Guanine; Humans; Hydroquinones; Male; Nitroparaffins; Oxidative Stress; Paraquat; Propane; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Smoking

2-Nitropropane (2-NP), a widely used industrial chemical, is a mutagen in bacteria and a powerful hepatocarcinogen in Sprague-Dawley rats. In contrast, 1-nitropropane (1-NP) is not mutagenic and does not appear to be carcinogenic. Thus far, the mechanism of carcinogenicity of 2-NP has not been examined. We report in the present work that i.p. treatment of male Sprague-Dawley rats with 100 mg/kg 2-NP results in a 3.6-fold increase (P less than 0.01) in the levels of 8-hydroxydeoxyguanosine as well as in the appearance of an additional electrochemically active species, presumably a modified deoxynucleoside, in liver DNA hydrolysates 6 h after dosing. Treatment with 2-NP also induces an 11-fold increase (P less than 0.0001) in the levels of 8-hydroxyguanosine in rat liver RNA, and results in the appearance of two new electrochemically active species (RX1 and RX2), presumably modified nucleosides. Small, statistically not significant increases of 8-hydroxyguanosine in RNA and of 8-hydroxydeoxyguanosine in DNA, as well as the induction of much smaller amounts of RX2 (but apparently not RX1) in rat liver RNA, are also observed following analogous treatment with 1-NP. Since the presence of 8-hydroxyguanine, a product of the attack of hydroxyl radicals (or other reactive oxygen species) on guanine, can cause DNA misreplication [Kuchino et al., Nature (Lond.), 327: 77-79, 1987], our findings are consistent with a mechanism of hepatocarcinogenicity of 2-NP based on damage to nucleic acids from the intracellular generation of reactive forms of oxygen and/or the 2-NP free radical.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Alkanes; Animals; Chromatography, High Pressure Liquid; Deoxyguanosine; DNA; DNA Damage; Free Radicals; Guanine; Liver; Nitroparaffins; Oxidation-Reduction; Propane; Rats; Rats, Inbred Strains; RNA; Time Factors