J. Biol. Chem., Vol. 261, Issue 25, 11585-11591, Sep, 1986
Monoclonal antibodies to thromboxane synthase from porcine lung. Production and application to development of a tandem immunoradiometric assay
RF Shen and HH Tai
Two hybridoma cell lines secreting antibodies against thromboxane synthase
of porcine lung were produced. Clone TS1 secretes IgG2a antibody of lower
affinity, while clone TS2 secretes IgG1 antibody of higher affinity. Both
antibodies (when bound to rabbit anti-mouse IgG- Staphylococcus aureus
complex) can immunoprecipitate thromboxane synthase from crude enzyme
preparations in an active form suggesting that binding was not directed at
the active site. Each antibody showed a distinctive pattern of
cross-reactivity with thromboxane synthase from different porcine tissues.
Neither of the antibodies cross-reacted with the enzyme from tissues of
other species tested, indicating the heterogeneous nature of the enzyme
among species. Competitive binding assay revealed that TS1 and TS2
recognized different determinants on the enzyme. The fact that two
antibodies bind to separate epitopes on the same enzyme allows the
development of a sensitive tandem immunoradiometric assay. The assay, based
on binding of 125I-TS2 to thromboxane synthase immobilized on TS1-S. aureus
complex, was linear with 7.5 approximately 75 ng of purified lung
thromboxane synthase as standards and applicable to enzyme preparations
regardless of their purity. The concentration of immunoreactive thromboxane
synthase in porcine tissues as determined by this assay followed the order
of platelet greater than colon greater than duodenum greater than lung
greater than kidney greater than stomach. The fact that gastrointestinal
tract is enriched with thromboxane synthase suggests that thromboxane may
have significant physiological roles to be recognized in these organs.