Abstract
Summary
We have determined the pepsin activity of canine gastric secretions (CGS) and of commercial crystalline porcine pepsin (CCPP) solutions at pH 1.8 (5 and 10 μg/ml) for various periods of time, at room temperature (23-28°), at refrigerator temperature (4°), in the freezing compartment of a refrigerator (—4°) and at —20°. Lowered activity was found under most of these conditions. The lower the temperature and the longer the time the greater is the loss. The CGS samples deviated somewhat from this general trend by showing some increases as well as decreases in activity at all temperatures except at 0°. We, therefore, recommend holding such samples in an ice bath at 0° for not longer than 3 hr, or addition of acidified glycerol for storage up to 1 day at —20°. Fresh preparations of CCPP solutions retained activity in an ice bath for up to 5 hr. If it is necessary to store CCPP solutions for a longer period of time—up to 6 days—addition of albumin or a combination of albumin and acidified glycerol is essential.
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