title: On the presence of serotonin in mammalian cardiomyocytes.
abstract: Pleiotropic effects of serotonin (5-HT) in the cardiovascular system are well documented. However, it remains to be elucidated, whether 5-HT is present in adult mammalian cardiomyocytes. To address this issue, we investigated the levels of 5-HT in blood, plasma, platelets, cardiac tissue, and cardiomyocytes from adult mice and for comparison in human right atrial tissue. Immunohistochemically, 5-HT was hardly found in mouse cardiac tissue, but small amounts could be detected in renal preparations, whereas adrenal preparations revealed a strong positive immunoreaction for 5-HT. Using a sensitive HPLC detection system, 5-HT was also detectable in the mouse heart and human atrium. Furthermore, we could identify 5-HT in isolated cardiomyocytes from adult mice. These findings were supported by detection of the activity of 5-HT-forming enzymes-tryptophan hydroxylase and aromatic L-amino acid decarboxylase-in isolated cardiomyocytes from adult mice and by inhibition of these enzymes with p-chlorophenylalanine and 3-hydroxybenzyl hydrazine. Addition of the first intermediate of 5-HT generation, that is 5-hydroxytryptophan, enhanced the 5-HT level and inhibition of monoamine oxidase by tranylcypromine further increased the level of 5-HT. Our findings reveal the presence and synthesis of 5-HT in cardiomyocytes of the mammalian heart implying that 5-HT may play an autocrine and/or paracrine role in the heart.
authors.affiliation: Medical Faculty, Institute of Pharmacology and Toxicology, Martin-Luther-University Halle-Wittenberg, Magdeburger Str. 4, 06112, Halle (Saale), Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Pönicke
authors.forename: Ulrich
authors.initials: U
authors.lastname: Gergs
authors.forename: Igor B
authors.initials: IB
authors.lastname: Buchwalow
authors.forename: Steffen
authors.initials: S
authors.lastname: Hauptmann
authors.forename: Joachim
authors.initials: J
authors.lastname: Neumann
mesh_terms: D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000311:Adrenal Glands / Q000166:cytology / Q000378:metabolism; D000818:Animals; D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism; D001792:Blood Platelets / Q000378:metabolism; D002478:Cells, Cultured; D010134:Fenclonine / Q000494:pharmacology; D006325:Heart Atria / Q000166:cytology; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D051379:Mice; D009206:Myocardium / Q000166:cytology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D012701:Serotonin / Q000096:biosynthesis / Q000097:blood / Q000378:metabolism*; D014364:Tryptophan / Q000378:metabolism; D014365:Tryptophan Hydroxylase / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D006834:Hydrazines; D012701:Serotonin; D014364:Tryptophan; C004297:3-hydroxybenzylhydrazine; D006916:5-Hydroxytryptophan; D014365:Tryptophan Hydroxylase; D001142:Aromatic-L-Amino-Acid Decarboxylases; D010134:Fenclonine