Abstract
Endothelial cells from bovine aorta and human umbilical vein and fibroblasts from human foreskin were cultured and subsequently evaluated for ability to metabolize serotonin (5βHT) to 5βhydroxyindoleacetic acid (5βHIAA). Cells were incubated for three hours with 4 Γ 10^β6^ M [^14^C] 5βHT creatinine sulfate. [^14^C] 5βHIAA was separated from labeled 5βHT by column chromatography and measured by scintillation counting. Production of 5βHIAA by bovine aorta cells was 39.0 Β± 7.5 (S.E.M., n = 6) nmoles per 10^9^ cells per hour. Production of 5βHIAA was markedly inhibited by the presence of 10^β4^ M iproniazid (an inhibitor of monoamine oxidase) or 10^β4^ M imipramine (an inhibitor of amine transport). 5βHIAA was the only product of 5βHT metabolism detected by thin layer chromatography. Production of 5βHIAA by human umbilical vein endothelial cells was 5.4 Β± 2.0 nmoles per 10^9^ cells per hour (n = 5) and by human foreskin fibroblasts was 3.9 Β± 1.4 nmoles per 10^9^ cells per hour (n = 5). The results obtained during incubation in the presence and absence of inhibitors indicate that bovine aorta endothelial cells maintained in tissue culture are able to transport serotonin with subsequent production of 5βHIAA. By contrast, human umbilical vein endothelial cells and fibroblasts exhibited relatively low rates of 5βHT uptake and metabolism.