Interactions in vitro and in vivo between dog trypsin and dog plasma protease inhibitors.

Trace amounts of dog trypsin mixed with dog serum or injected i.v. into the dog were bound mainly to the a-macroglobulins (82 per cent) and to α1-antitrypsin (18 per cent). The relative affinity of dog trypsin for the α-macroglobulins was about 30 times as high as for the other inhibitors taken together. Dog trypsin bound to α1-antitrypsin was rapidly taken over by the α-macroglobulins in vitro as well as in vivo. The trypsin-α-macroglobulin complexes injected i.v. or formed in vivo were rapidly eliminated from the blood stream following a first order reaction, while α1-antitrypsin-bound trypsin disappeared much slower as found for bovine trypsin and dog plasma trypsin inhibitors.