Abnormal forearm vascular responses in the carcinoid syndrome: the role of kinisns and kinin-generating system.

Abstract

The effects of bradykinin, epinephrine, and reflex stimulation of the sympathetic nervous system on the arteries and veins of the forearm were studied and compared in 10 normal subjects and 8 patients with carcinoid tumors. Forearm blood flow was measured with a strain gauge plethysmograph, forearm vascular resistance was calculated and venous tone was assessed by a venous occlusion technique. Bradykinin-induced flushes resulted in dilatation of the arteries and veins in both groups of individuals. Epinephrine produced flushes only in the carcinoid patients and resulted in more arteriolar dilatation and less venous constriction than in the normal subjects. Cold stimulation produced flushes and an attenuated vascular constrictor response in the majority of carcinoid patients. Arteriolar dilatation was observed during spontaneous flushes in patients with carcinoid tumors. Elevations of peripheral arterial blood concentrations of bradykinin peptide and anionic kallikrein were detected during flushes provoked by these interventions. This investigation provides additional evidence implicating the kallikrein-bradykinin system in the production of the carcinoid flush and in the modification of vascular responses to standard stimuli.