IRS1 and Insulin resistance: Phosphorylation of insulin receptor substrate 1 (IRS1) at serine 307 in liver tissue, which has been associated with insulin resistance (Koketsu et al. 2008), was significantly higher in male offspring of the 2.0 mg/kg Cd and Hg treatment group (p < 0.05; mean ratio of p-IRS1 to total IRS1 0.66 ± 0.04, n = 17 mice) than in vehicle controls (0.30 ± 0.04, n = 11 mice).