The biliary excretion of trypsin in rats

The serum half-life of bovine [³H]acetyltrypsin was estimated to be 9 rain following intravenous administration in rats. This was maintained when six successive doses of 200 g each were given at 1-h intervals. The enzyme was removed from the circulation after complexing with 2-macroglobulin (2-M). The amount of³H label appearing in bile increased with each successive dose and this was associated with breakdown products (<10 000 daltons) of the ₂–M/[³H] acetyltrypsin. Intact –M/[³H] acetyltrypsin was recovered from bile but represented only 0.06% of the administered dose of active enzyme.