THE ENZYMATIC INACTIVATION OF CHOLECYSTOKININ BY BLOOD SERUM

Abstract

Blood serum had the prop-erty of inactivating or destroying secretin enzymatically. The presence of a similar mechanism for the re-moval of active cholecystokinin from the circulation was studied by incubation of standard amts. of a chole-cystokinin concentrate with blood serum under various conditions of time, temp., pH, and conc, of serum. The contractile response of the cannu-lated gall-bladder to such incubation mixtures was compared with that elicited by control injs., and it was found that serum possessed the prop-erty of inactivating cholecystokinin. Such inactivation was progressive with time and occurred most rapidly at body temp. The agent involved was heat labile, and was effective only at a reaction approx. the pH of the blood. Thus, the mechanism whereby inactivation occurred was an enzymic one. The enzyme involved might be secretinase. The inactivation of cholecystokinin proceeded considerably more slowly than did that of secretin.