Cell Proliferation in Carcinoid Valve Disease: A Mechanism for Serotonin Effects
Nalini M. Rajamannan MD, Noel Caplice MD, Fenny Anthikad MD, Thomas J. Sebo MD, Thomas A. Orszulak MD, William D. Edwards MD, Jamil Tajik MD, Robert S. Schwartz MD

The study aim was to assess the direct proliferative effect of serotonin on porcine aortic subendothelial valve cells in vitro. The study also determined the presence of proliferation in surgically removed human valves with carcinoid heart disease versus normal human valves. Confirmation of serotonin-induced proliferation was demonstrated by thymidine incorporation and inhibition of proliferation with a serotonin antagonist. Increased proliferation and 5HT1b receptors were present in the human carcinoid valves as opposed to the normal control cardiac valves. Direct stimulation of serotonin on cardiac valve tissue via serotonin receptors may play an important role in the proliferative lesion found in carcinoid heart disease.