Epx^tm1Nal

Exons 6-8 were replaced with a PGK-neo cassette via homologous recombination. These exons encode conserved histidine and arginine residues essential to catalytic activity, 6 half-cysteine residues involved in disulfide linkages, and 11 residues located near the heme prosthetic group. RT-PCR analysis revealed the absence of gene expression in various tissues from homozygous mutant animals. Loss of eosinophil peroxidase (EPO) activity in homozygous mutant mice was verified by 1) cytochemical staining of peritoneal cavity exudate cells recovered after sensitization/challenge of mice with a whole-protein extract from the helminth M. corti, and 2) an endpoint colorimetric assay detecting EPO in lysates of the peritoneal cavity exudates. In addition, loss of EPO activity was functionally demonstrated by assessing an EPO-specific oxidation product, bromotyrosine, in whole-lung homogenates from mutant mice using an OVA i.p. sensitization/aerosol challenge model of respiratory inflammation. (J:70567)