| First Author | Mathar I | Year | 2014 |
| Journal | Circ Res | Volume | 114 |
| Issue | 2 | Pages | 283-94 |
| PubMed ID | 24226423 | Mgi Jnum | J:223624 |
| Mgi Id | MGI:5659827 | Doi | 10.1161/CIRCRESAHA.114.302835 |
| Citation | Mathar I, et al. (2014) Increased beta-adrenergic inotropy in ventricular myocardium from Trpm4-/- mice. Circ Res 114(2):283-94 |
| abstractText | RATIONALE: The Trpm4 gene has recently been associated with several disorders, including cardiac conduction diseases and Brugada syndrome. Transient receptor potential member 4 (TRPM4) proteins constitute Ca2+ -activated, but Ca2+ -impermeable, nonselective cation channels and are expressed both in atrial and in ventricular cardiomyocytes. The physiological function of TRPM4 in the heart remains, however, incompletely understood. OBJECTIVE: To establish the role of TRPM4 in cardiac muscle function. METHODS AND RESULTS: We used TRPM4 knockout mice and performed patch-clamp experiments, membrane potential measurements, microfluorometry, contractility measurements, and in vivo pressure-volume loop analysis. We demonstrate that TRPM4 proteins are functionally present in mouse ventricular myocytes and are activated on Ca2+ -induced Ca2+ release. In Trpm4(-/-) mice, cardiac muscle displays an increased beta-adrenergic inotropic response both in vitro and in vivo. Measurements of action potential duration show a significantly decreased time for 50% and 90% repolarization in Trpm4(-/-) ventricular myocytes. We provide evidence that this change in action potential shape leads to an increased driving force for the L-type Ca2+ current during the action potential, which explains the altered contractility of the heart muscle. CONCLUSIONS: Our results show that functional TRPM4 proteins are novel determinants of the inotropic effect of beta-adrenergic stimulation on the ventricular heart muscle. |
