Evidence for synthesis and release of catecholamines by human amniotic epithelial cells

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Abstract
THE present study investigated the presence, possible synthesis and release of catecholamines (CA) by human amniotic epithelial cells (HAEC) using HPLC with electrochemical detection. The presence of CA was indicated by the detection of norepinephrine (NE), dopamine (DA) and its metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) in extracts of cultured HAEC. Incubation of HAE cells in medium supplemented with l-tyrosine (CA precursor) and tetrahydrobiopterin (tyrosine hydroxylase cofactor) significantly increased the production of catecholamines, suggesting CA synthesis by HAEC. In contrast, pharmacological inhibition of tyrosine hydroxylase by α-methyl- p-tyrosine (MPT) significantly reduced CA production, further confirming CA synthesis by HAEC. Catecholamines were also detected in the cell incubation media, demonstrating the ability of HAEC to spontaneously secrete CA. Moreover, incubation of cells with 50 mM K+ for 10 min increased the amount of CA released into the medium. Additionally, the detection of DOPAC, a primary metabolite of DA, in HAEC strongly indicates that these cells contain DA metabolizing enzymes. The present results suggest that HAEC synthesize and release CA. These cells may be a possible candidate for transplantation therapy of neurodegenerative diseases such as Parkinson's disease and also may serve as a model to study the aspects of catecholaminergic activity.