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Abstract
DNA single‐strand breaks induced by procarcinogens were detected in Chinese hamster ovary (CHO) cells cocultured with adult rat hepatocytes. Freshly isolated adult rat hepatocytes were added to the CHO cell culture prelabeled with [3H]thymidine. After allowing the hepatocytes to attach on or near the CHO cells, aflatoxin B1 or benzo[a]‐pyrene was added to the culture and incubated for the desired time. DNA single‐strand breaks in CHO cells were measured by the alkaline elution technique. Aflatoxin B1 induced some DNA single‐strand breaks in CHO cells cultured alone, but in coculture system with hepatocytes the number of DNA single‐strand breaks increased greatly. The magnitude of the increase was related to the dose and the time of exposure to aflatoxin B1. Addition of proteinase‐K to the cell lysates increased the elution of DNA compared to that of samples without proteinase‐K. Benzo[a]pyrene did not induce any DNA single‐strand breaks in CHO cells in the absence of liver cells, but a significant number of single‐strand breaks were detected in the coculture system.