Properties and catabolism of heat treated antithrombin III concentrate

Heat treatment is employed to diminish the transmission of hepatitis when blood products are administered. It is possible that such a procedure could reduce the biological activity of the proteins and induce changes in structure and aggregation state. We have therefore made in vitro and pharmacokinetic studies of heat treated antithrombin III (AT III) concentrate using both radiolabelled and non-labelled preparations. The purification, heat treatment and the radiolabelling procedures did not induce any changes in the AT III molecules with exception of a decrease in heparin affinity in about 10% of the molecules. The in vivo studies using 125I AT III showed that the fractional catabolic rate was increased and the half-life was shortened by about 20-25% compared to our previous studies on non-heat treated AT III concentrate. Our present findings indicating a mean half-life of 3.0 days are quite comparable to studies by others on non-heat treated AT III, however.