In vivo repair of rat liver DNA damaged by 3-hydroxyxanthine.

Using alkaline and neutral sucrose gradients, it was observed that administration of the hepatocarcinogen, 3-hydroxyxanthine, to rats, resulted in the slower sedimentation of liver DNA in alkaline and neutral sucrose gradients. Slower sedimentation of liver DNA in alkaline sucrose gradients was apparent within 4 h following the administration of the carcinogen at a dose of 50 mug/g body weight. The fragmentation of liver DNA was progressive with an increase in the dose. Such fragmentation caused by a dose of 100 mug/g was largely repaired by 24 h following the administration of the carcinogen. Fragmentation and repair of liver DNA with a dose of 100 mug or more/g body weight was also seen using neutral sucrose gradients. In neutral sucrose gradients significant repair of the fragmented DNA was seen by 24 h after carcinogen. Liver DNA from rats given 3-hydroxyxanthine (100 mug/g for 4 h) or calf thymus DNA incubated in vitro with this carcinogen did not show any change in their melting profile.