A nonlinear dosimetric model for hemoglobin adduct formation by the neurotoxic agent acrylamide and its genotoxic metabolite glycidamide.

Hemoglobin (Hb) adducts, formed by the neurotoxic agent acrylamide (AA) and its genotoxic metabolite glycidamide (GA), were measured in the rat by means of a method for simultaneous determination of the adducts formed to cysteine. A novel, nonlinear dosimetric model was developed to describe Hb adduct formation. This model incorporates the saturable kinetics of the metabolic conversion in vivo of AA to GA. The pharmacokinetic parameters Vmax and Km and the first-order rates of elimination, k1 and k2, for AA and GA from all processes except conversion of AA to GA, were estimated directly from Hb adduct data to 19 M hr-1, 66 microM, 0.21 hr-1, and 0.48 hr-1, respectively. At low concentrations, approximately 60% of AA was metabolized to GA. The nonlinear dosimetric model for adduct formation has potential general applicability in high-to-low-dose extrapolation of genotoxic effects.