Long-term serotonin administration induces heart valve disease in rats.
BACKGROUND
The purpose of this study was to investigate whether rats dosed with serotonin develop changes similar to those seen in human carcinoid heart disease.


RESULTS
Ten Sprague-Dawley rats were given serotonin injections subcutaneously once daily for 3 months; controls were given saline. A long-lasting hyperserotoninemia with a >10-fold increase in both platelet-poor plasma and dialysate from the femoral muscles appeared. The animals developed clinical signs such as flushing and loose stools. After 3 months, 6 of 10 rats given serotonin had pathological echocardiographs. Two animals had a combination of aortic and pulmonary valve insufficiency, 1 had isolated aortic valve insufficiency, and 3 had isolated pulmonary valve insufficiency. Histopathological examination revealed shortened and thickened aortic cusps and carcinoidlike plaques characterized by a collection of myofibroblasts within an extracellular matrix of collagen ground substance. Immunostaining for Ki-67 demonstrated an increased number of proliferating subendocardial cells. In the control group, no pathological changes were seen. With the use of reverse-transcription polymerase chain reaction, normal rat aortic cusps were shown to express mRNA for serotonin receptors 5-HT1A, 5-HT2A, and 5-HT2B and the serotonin transporter 5-HTT.


CONCLUSIONS
For the first time, long-term serotonin administration was performed in rats. Morphological and echocardiographic changes similar to those seen in human carcinoid heart disease developed. This study demonstrates that serotonin most likely is involved in the pathogenesis of carcinoid heart disease.
Gustafsson
Björn I
BI
Department of Internal Medicine, St Olavs Hospital HF, Trondheim University Hospital, Trondheim, Norway. bjorn.gustafsson@medisin.ntnu.no
Tømmerås
Karin
K
Nordrum
Ivar
I
Loennechen
Jan P
JP
Brunsvik
Anders
A
Solligård
Erik
E
Fossmark
Reidar
R
Bakke
Ingunn
I
Syversen
Unni
U
Waldum
Helge
H
D000818:Animals; D002275:Carcinoid Heart Disease / Q000139:chemically induced / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D004562:Electrocardiography; D005109:Extracellular Matrix / Q000737:chemistry; D005347:Fibroblasts / Q000473:pathology; D006349:Heart Valve Diseases / Q000139:chemically induced* / Q000473:pathology; D019394:Ki-67 Antigen / Q000032:analysis; D008562:Membrane Glycoproteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000235:genetics; D012701:Serotonin / Q000008:administration & dosage* / Q000097:blood / Q000494:pharmacology; D050486:Serotonin Plasma Membrane Transport Proteins; D013997:Time Factors
D019394:Ki-67 Antigen; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D011985:Receptors, Serotonin; D050486:Serotonin Plasma Membrane Transport Proteins; C493232:Slc6a4 protein, rat; D012701:Serotonin