RESUMEN
Objective Studies are rarely reported on the relationship of the sympathetic pathway mediated by alpha 1-AR with the expression of the natriuretic peptide and regulation of its activity. Our research aimed to observe the effect of phenylephrine (PE) on the expression of natriuretic peptides and explore the mechanism of phenylephrine acting on the expressions of the atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) as well as their relationships with Calcineurin (CaN)-NFATc3 and MEK3-P38 MAPK signaling pathways.Methods Neonatal rat cardiomyocytes were isolated and cultured in vitro for 72 hours, and then divided into five groups: control, PE, prazosine (Praz)+PE, calcineurin inhibitor cyclosporine (CsA) pretreatment+PE, and P38 MAPK inhibitor SB203580 pretreatment+PE, and treated with respective agents. The proliferation of the cardiomyocytes was determined by trypan blue counting and MTT assay, their viability detected by colorimetry, the protein expressions of ProANP, ProBNP, Calcineurin A and p-P38 MAPK measured by Western blot, and the contents of the NFATc3 (T cell activating transcription factor 3) and MEK3 (MAP2K3, mitogen-activated protein kinase family) examined by ELISA.Results After treatment, the cardiomyocytes in the Praz+PE group were sparsely arranged, with nuclear pyknosis and no regular beating, those in the CsA+PE group exhibited poikilocarynosis, with bright margins and cord-like fibers, and those in the SB203580+PE group, the cytoplasm was lightly stained, with slight fragmentation and lots of dead cells. The A value was increased in the PE group (0.78±0.09) as compared with the control, but decreased in the Praz+PE, CsA+PE and SB203580+PE groups (0.31±0.09, 0.47±0.12 and 0.42±0.14) (P<0.05), significantly lower in the Praz+PE, CsA+PE and SB203580+PE than in the PE group (P<0.05), but higher in the CsA+PE and SB203580+PE than in the Praz+PE group (P<0.05). The expressions of the ProANP and ProBNP proteins in the cardiomyocytes were remarkably upregulated in the PE group as compared with those in the control (P<0.01) but suppressed in the other three groups (P<0.05), significantly lower in the Praz+PE, CsA+PE and SB203580+PE than in the PE group (P<0.05), but higher in the CsA+PE and SB203580+PE than in the Praz+PE group (P<0.05). The expressions of the CaN and p-P38 proteins in the cardiomyocytes were elevated in the PE group as compared with those in the control (P<0.05) but reduced in the other three groups (P<0.05), significantly lower in the Praz+PE, CsA+PE and SB203580+PE than in the PE group (P<0.05), while that of CaN markedly higher in the CsA+PE and SB203580+PE than in the Praz+PE group (P<0.05) and that of p-P38 higher in the CsA+PE than in the Praz+PE group (P<0.05). The expressions of the NFATc3 and MEK3 in the cardiomyocytes were increased in the PE group as compared with those in the control (P<0.05) but decreased in the other three groups (P<0.05), significantly lower in the Praz+PE, CsA+PE and SB203580+PE than in the PE group (P<0.05), but higher in the CsA+PE and SB203580+PE than in the Praz+PE group (P<0.05).Conclusion Phenylephrine can activate the ANP and BNP sympathetic signaling pathways, and CaN-NFATc3 and MEK3-P38 related signaling pathways may be involved in α1-adrenergic receptor-mediated endocrine hormone (ANP/BNP) expressions in isolated cardiomyocytes.