Quantification of pepsin A activity in canine and rat gastric juice with the chromogenic substrate azocoll.
The activity concentration of pepsin may be quantified by using azocoll as a chromogenic substrate. The measured enzyme activity is constant between pH 1.2 and 3.4 and is proportional (r = 0.61) to the activity measured with hemoglobin as substrate. The activity of purified porcine pepsin is inhibited by pepstatin A with an apparent Ki of 115 nmol/L. The azocoll method is useful for measuring changes in pepsin secretion in response to pharmacological agents. For example, pepsin activity of canine gastric juice is decreased by 80% after in vivo administration of 0.5 mg of the synthetic trimethyl prostanoid Ro 22-6923 per kilogram of body weight. The method is sufficiently sensitive to measure the pepsin activity in 0.2 microL of canine gastric juice with a CV of approximately 10%, is simpler than the hemoglobin-substrate methods, and the substrate is commercially available.
D000818:Animals; D001391:Azo Compounds; D003094:Collagen; D004396:Coloring Agents; D004285:Dogs; D005260:Female; D005750:Gastric Juice / Q000201:enzymology*; D006454:Hemoglobins / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008722:Methods; D010434:Pepsin A / Q000378:metabolism*; D010436:Pepstatins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013552:Swine
D001391:Azo Compounds; D004396:Coloring Agents; D006454:Hemoglobins; D010436:Pepstatins; C014195:Streptomyces pepsin inhibitor; C028470:Azocoll; D003094:Collagen; D010434:Pepsin A; C031375:pepstatin