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Evidence of Repair of DNA Damage Induced by 4-Hydroxyaminoquinoline 1-Oxide in Guinea Pig Pancreatic Slices in Vitro¹

Environmental Health Programs, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106

In vitro exposure of guinea pig pancreatic slices to 4-hydroxyaminoquinoline 1-oxide (HAQO) resulted in increased [methyl-³H]thymidine ([³H]TdR) incorporation into DNA, both in the presence and absence of hydroxyurea (HU). Normal DNA replicative synthesis, but not DNA repair synthesis, was suppressed by HU. The increase in [³H]TdR incorporation into DNA, in the presence of HU, represented DNA repair synthesis in response to DNA damage induced by HAQO. Exposure of pancreatic slices to 10^-6 to 10^-5 M concentrations of HAQO did not significantly increase thymidine incorporation; however, a 15-min exposure to 10^-4 M HAQO induced a significant increase in HU-insensitive [³H]TdR incorporation into DNA. Kinetics of [³H]TdR incorporation suggests that most of the DNA repair synthesis occurs during the 2 hr following HAQO-induced DNA damage.

¹ Supported by Contract NO1-CP-23284 from the National Cancer Institute, Bethesda, Md.

Received 8/13/75. Accepted 12/ 5/75.