The production of ATIII using Se-75-selenomethionine as a tracer was studied. After i. v. injection of 100μCi of Se-75-selenomethionine, blood samples were obtained using 3.8% sodium citrate as anticoagulant at the following times: 10min, 1, 2, 3, 4, 5, 6hours, 1, 2 and 3 days. One ml of plasma (56°C, 3min heat defibrinated) was incubated for 1hour with 1ml of anti-canine ATIII rabbit antiserum at 37°C. Then the mixture was stood for 24 hours at 4°C. The precipitate was separated by centrifugation and was washed 3 times with 0.05 Mol phosphate buffer (pH 8.0). The radioactivity of the precipitate was measured.
Using I-125-ATIII as a tracer, about 90% of the total radioactivity was recovered in the precipitate in the case of mixture of equal amount of canine plasma and antiserum.
1) In normal 4 dogs, the radioactivity incorporated to ATIII was increased rapidly and reached the maximum 6 hours after the injection of Se-75-selenomethionine. The maximum radioactivity was 970±55.0cpm/mg ATIII.
2) In the case of Se-75-selenomethionine being injected 24 hours after Endotoxin (E. coli. 026: B6) 1mg/kg infusion, the maximum radioactivity incorporated into ATIII was observed 3 hours after the Se-75-selenomethionine injection and was 2.8 times high as compared with normal values.
These results indicate that this method using Se-75-selenomethionine as a tracer is useful to study of ATIII production.
