A Simple, Quantitative Method for Titration of Trypsin and Trypsin Inhibitors.

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Abstract
A technically simple, rapid method, called the film-gelatin digestion method, for the quantitative titration of tryptic enzymes and of the inhibitors of tryptic activity in serum or other fluids is described. The procedure is especially designed to permit critical tests to be performed routinely on a large scale. Originally developed for study of the role of antitrypsin in the antianaphylactic state, it may serve also for investigation of various physiologic and pathologic conditions, other than hypersensitivity, in which protease inhibitors appear to play a vital part. Strips of an especially prepared photographic film of uniform density and hardness are immersed in buffered solns. of crystalline trypsin, and in mixtures of graded trypsin dilutions with the serum (or other fluid) under test, and incubated at 40[degree]C for a constant time (about 6 min.). Titrations may also be carried out by mixing serial dilutions of the specimen with a constant amt. (one tryptic unit) of standard trypsin soln. The procedure utilizes materials and technics familiar to serologists, rather than to skilled biochemists only, and gives definitive, reproducible results that can be expressed in simple figures. A feature is provision for the making of a permanent record of each titration by mounting discs cut from the film-strips after completion of a test on a white filing card which bears appropriate descriptive data. Since the reagents (including the stock trypsin in solns.) are stable, and all conditions of the tests are readily standardized, strictly comparable figures can be obtained in separate expts. conducted in the same or in different laboratories at any time.
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