Nitric oxide, a key signaling molecule in the murine early embryonic heart

• Published in: The FASEB journal 2004-07, Vol.18 (10), p.1108-1110
• Main Authors: Malan, Daniela, Ji, Guanju, Schmidt, Annette, Addicks, Klaus, Hescheler, Jürgen, Levi, Renzo C., Bloch, Wilhelm, Fleischmann, Bernd K.
• Format: Article
• Language: English
• Subjects: Animals; Animals, Outbred Strains; Calcium - metabolism; Calcium Channels, L-Type - metabolism; Carbachol - pharmacology; Cholinergic Agents - pharmacology; Cyclic AMP-Dependent Protein Kinase Type II; Cyclic AMP-Dependent Protein Kinases - pharmacology; embryonic development; Female; Fetal Heart - physiology; Guanylate Cyclase - antagonists & inhibitors; Guanylate Cyclase - pharmacology; Heart Ventricles - cytology; Heart Ventricles - embryology; Ion Transport - drug effects; Mice; Mice, Knockout; muscarinic signaling; Myocytes, Cardiac - drug effects; Myocytes, Cardiac - metabolism; Nitric Oxide - physiology; Nitric Oxide Synthase - genetics; Nitric Oxide Synthase - physiology; Nitric Oxide Synthase Type II; Nitric Oxide Synthase Type III; omega-N-Methylarginine - pharmacology; Pertussis Toxin - pharmacology; Phosphodiesterase Inhibitors - pharmacology; Receptors, Muscarinic - drug effects; Receptors, Muscarinic - physiology; regulation of ICa; Signal Transduction - drug effects; Signal Transduction - physiology; ventricular cardiomyocytes
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fj.03-1158fje

ABSTRACT Nitric oxide (NO) is thought to play an important role as a signaling molecule in embryonic and adult cardiomyocytes; however, its involvement in muscarinic signaling is still unclear. The aim of the present work was to analyze the muscarinic modulation of the L‐type Ca2+ current (ICa) in early‐ and late‐stage embryonic ventricular cardiomyocytes. Muscarinic stimulation depressed basal ICa by 30.1 ± 3.2% (n=27) in early‐stage cardiomyocytes. Pharmacological evidence suggested that the muscarinic modulation was mediated through generation of NO, activation of cGMP‐dependent phosphodiesterase (PDE) 2, and ensuing lowering of cyclic AMP/protein kinase A (cAMP/PKA) levels. Conversely, in late‐stage cardiomyocytes, muscarinic regulation of ICa occurred in a NO‐independent manner via inhibition of prestimulated adenylyl cyclase (AC). To unequivocally prove the involvement of NO and to identify the nitric oxide synthase (NOS) isoform(s), we analyzed muscarinic signaling in embryonic ventricular cardiomyocytes of NOS2 (–/–) and NOS3 (–/–) mice. The early‐stage NOS3 (–/–) cardiomyocytes lacked muscarinic modulation, whereas it was preserved in NOS2 (–/–) cells. Moreover, at the late embryonic stage, muscarinic modulation of ICa was intact in both strains. Thus, NO is the key regulator of muscarinic signaling in the early embryonic ventricle, whereas at later stages, signaling occurs through a NO‐independent pathway.