Myeloperoxidase (MPO) Assay

Colonic MPO levels were measured to determine the degree of neutrophil infiltration. The colon was weighed and homogenized in 50 mM hexadecyl trimethyl ammonium bromide (HTAB) - 50 mM potassium phosphate (pH 6.0) buffer. The homogenate was centrifuged at 13,400 × g for 6 min at 4 °C. The supernatant was collected or restored at -80 °C until use. 7 μL of tissue homogenate was mixed with 200 μL of reaction buffer (16.7 mg/mL o-dianisidine dihydrochloride, 50 mM potassium phosphate buffer [pH 6.0], 0.0006% H₂O₂) and was read at 450 nm using a spectrophotometer at 30 s intervals as previously performed ²⁸.