The MPO activity assay in homogenates of rat liver tissues was measured as described previously (4 (link)). Frozen liver tissue samples were thawed and suspended in pH 6.0 phosphate buffer containing 0.5% hexadecyltrimethylammonium bromide (Sigma, St. Louis, Mo). All samples were sonicated on ice, centrifuged at 12,000 × g for 15 min at 4°C, and then aliquots were transferred into phosphate buffer (pH 6.0) containing 0.167 mg/mL O-dianisidine hydrochloride and 0.0005% hydrogen peroxide (Sigma). The change in absorbance was measured at a wavelength of 460 nm with a spectrophotometer for 5 min. MPO activity was calculated using a standard curve generated using human MPO (Sigma), and values were normalized according to the protein concentration.