Arginine vasopressin-mediated cardiac differentiation - Insights into the role of its receptors and nitric oxide signaling

Despite the existence of a functional arginine vasopressin ( AVP) system in the adult heart and evidence that AVP induces myogenesis, its significance in cardiomyogenesis is currently unknown. In the present study, we hypothesized a role for AVP in cardiac differentiation of D3 and lineage-specific embryonic stem ( ES) cells expressing green fluorescent protein under the control of atrial natriuretic peptide ( Anp) or myosin light chain-2V ( Mlc-2V) promoters. Furthermore, we investigated the nitric oxide ( NO) involvement in AVP-mediated pathways. AVP exposure increased the number of beating embryoid bodies, fluorescent cells, and expression of Gata-4 and other cardiac genes. V1a and V2 receptors ( V1aR and V2R) differentially mediated these effects in transgenic ES cells, and exhibited a distinct developmentally regulated mRNA expression pattern. A NO synthase inhibitor, L-NAME, powerfully antagonized the AVP-induced effects on cardiogenic differentiation, implicating NO signaling in AVP-mediated pathways. Indeed, AVP elevated the mRNA and protein levels of endothelial NO synthase ( eNOS) through V2R stimulation. Remarkably, increased beating activity was found in AVP-treated ES cells with down-regulated eNOS expression, indicating the significant involvement of additional pathways in cardiomyogenic effects of AVP. Finally, patch clamp recordings revealed specific AVP-induced changes of action potentials and increased L-type Ca2+ ( I-Ca,I- L) current densities in differentiated ventricular phenotypes. Thus, AVP promotes cardiomyocyte differentiation of ES cells and involves Gata-4 and NO signaling. AVP-induced action potential prolongation appears likely to be linked to the increased I-Ca,I- L current in ventricular cells. In conclusion, this report provides new evidence for the essential role of the AVP system in ES cell-derived cardiomyogenesis.