Flushing in the carcinoid syndrome and plasma kallikrein.

To examine the role of kallikrein in the etiology of flushing in the carcinoid syndrome, chromogenic substrates specific for kallikrein were used to measure two isoenzymes of this substance. The plasma and glandular kallikrein levels were determined in 20 carcinoid patients and in 17 controls. Kallikrein levels were not significantly different between these two groups. Twelve carcinoid patients and six controls were given alcohol and the kallikrein activity was measured before and at 2, 5, and 10 minutes after alcohol ingestion; kallikrein activity did not change significantly. Kallikrein was absent from the primary tumors of seven patients with carcinoids. These studies, therefore, indicate that kallikrein with subsequent induction of bradykinin formation is not solely responsible for the flushing in the carcinoid syndrome.