5-Hydroxytryptamine synthesis in HL-1 cells and neonatal rat cardiocytes

Abstract Some reports showed that serotonergic system might have existed and that 5-hydroxytryptamine (5-HT) was detected in the hamster heart. The source of 5-HT in the heart, however, remains to be fully elucidated. So the present study was designed to define serotonergic system and to clarify which cell could produce 5-HT in the heart. As a result, 5-HT was detected in homogenates of HL-1 cardiomyocytes by high performance liquid chromatography with fluorescence detection, but not in those of neonatal rat non-cardiomyocytes (NMCs). And TPH and AADC mRNAs were expressed in HL-1 cardiomyocytes and neonatal rat cardiomyocytes (MCs), not in NMCs. mRNAs of 5-HT 2A receptor were detected in both MCs and NMCs, and those of 5-HT 2B receptor in NMCs. These findings definitively demonstrate that 5-HT is secreted from the myocytes of the heart and strongly implied that 5-HT might play a certain role in cardiac physiology. Ó 2005 Elsevier Inc. All rights reserved. Keywords: 5-Hydroxytryptamine; HL-1 cardiomyocytes; Neonatal rat cardiac myocytes; Neonatal rat cardiac non-myocytes; HLPC Several studies reported that 5-HT was demonstrated in the hamster heart and involved in cardiac pathophysiology [1-4]. We previously showed that sarpogrelate, a specific inhibitor of 5-HT 2A receptor, attenuated [ 3 H]leucine uptake into neonatal Wistar rat ventricular cardiac myocytes (MCs) but failed to show the evidence of 5-HT secretion from MCs Materials and methods All experiments were performed in accordance with the Guidelines on Animal Experimentation of Jikei University. Preparation of HL-1 cardiomyocytes. HL-1 cardiac myocytes (passages 72-73