A Benchmark analysis of acrylamide-derived DNA adducts in rat hepatocytes in culture measured by a new, highly sensitive method

Acrylamide (AA) is a carcinogen formed during thermal food processing and can cause tumors in rodents while its carcinogenic potency in humans is unclear. Metabolism of AA, preferentially in the liver, leads to glycidamide (GA) forming N7-GA-guanine (N7-GA-Gua) as the major AA-derived DNA adduct in rodents. Here, a novel method allowing high sensitivity by avoidance of major matrix effects was applied to analyze N7-GA-Gua levels in nuclear DNA from rat hepatocytes in primary culture. We could thus for the first time detect a background level of 5-10 adducts/10(8) nucleosides in untreated hepatocytes. Incubation with AA did not result in a statistically significant increase in adduct levels over background up to a substrate concentration of 500 mu M although a trend to slightly higher adduct levels was observed at and above 200 mu M AA. At concentrations > 500 mu M significant increases in N7-GA-Gua levels were found. When Benchmark concentration (BMC) modeling was applied to the data, non-linear concentration-response curves were obtained suggesting that AA started to cause measurable increases over background of N7-GA-Gua levels above certain concentrations only. Calculation of the composite BMCL10 (Lower Bound of a 95 % confidence interval) of a BMC leading to a 10 % increase of N7-GA-Gua levels over background resulted in a value of 6.35 mu M AA after 24 h. A concentration below this value cannot be expected to lead to an increase in N7-GA-Gua of more than 10 % over the background seen in untreated hepatocytes.