Abstract
Summary
A rapid microcolorimetric meth-od for measurement of plasma histaminase has been described. Its lower limit of sensitivity is 0.1 mμM histamine oxidized/ml of plasma/minute and its reproducibility, ± 0.1 mμM. In a series of mammalian species surveyed, no activity was detected in the plasma of mice and rats; plasma from guinea pigs, dogs, squirrel monkeys, and man exhibited relatively low activities; plasma activity of rabbits and cats was somewhat higher; plasma from rhesus monkeys was more active than that of any other species. Studies of pH optimum, aminoguanidine and substrate inhibition, and substrate specificity using human plasma indicate that the primary activity measured was histaminase activity.
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