[Determination of the base contents of liver DNA of rats by reversed-phase high performance liquid chromatography].

The base contents of liver deoxyribonucleic acid (DNA) of rats living at an altitude of 2.3 km were determined by reversed-phase high performance liquid chromatography. At first, 0.05 mol/L KH2PO4(pH 4.0) was used to dissolve the DNA acid hydrolysis products with 8-bromoguanosine (Br8G) as an internal standard. Then the DNA hydrolysis products with Br8G were chromatographed on a Supelcosil LC-18 column with UV detection at 254 nm and eluted by the mobile phase of MeOH-0.05 mol/L KH2PO4(pH 4.0) (20:80, V/V) at the flow rate of 0.8 mL/min. Under these conditions, several bases were separated effectively. From the results, the relatively constant proportions of the bases in DNA were found. The contents were 17.4% of cytosine (C), 28.8% of adenine (A), 23.3% of guanine (G) and 25.3% of thymine (T). RSDs of the determination of these bases were 1.7%, 1.5%, 1.3% and 2.1%, respectively. At the same time the methylation level of liver DNA of the rats determined by the internal standard method was 6.2%.