Evidence for the release of bradykinin in carcinoid syndrome.

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Abstract
The kinin peptide released during carcinoid flushes was characterized with gradient elution and paper chromatography, electrophoresis, enzymatic inactivation rates, and studies on its pharmacologic effects. All of these investigations indicated that the carcinoid kinin was bradykinin. It is postulated that carcinoid tumors release the kinin-forming enzyme kallikrein in response to stimuli such as epinephrine. This enzyme splits lysyl-bradykinin from a protein substrate in plasma, and the lysylbradykinin is then converted rapidly to bradykinin. The possible relation of bradykinin to the patho-physiology of the carcinoid syndrome is discussed, and it is suggested that bradykinin may be released from normal enterochromaffin cells by physiologic stimuli.