Effect of PKC ε Isoform in AVP Regulating the MLC20 Phosphorylation of SMA After Shock and MLCP/MLCK Activity of VSMC

OBJECTIVE The present study was aimed to investigate the roles of protein kinase C (PKC) ε isoform in the regulation of arginine vasopressin (AVP) on myosin light chain (MLC20) phosphorylation of vascular smooth muscle after shock, and myosin light chain phosphatase (MLCP) and myosin light chain kinase (MLCK) activity of vascular smooth muscle cell (VSMC) after hypoxia. METHODS With hemorrhagic shock model from rats and hypoxia-treated VSMC，the effects of PKC ε isoform in AVP regulating the phosphorylation of MLC20 of superior mesenteric artery (SMA) after shock, and the activity of MLCP/MLCK in VSMC were observed. RESULTS The MLC20 phosphorylation of SMA following hemorrhagic shock was significantly decreased, and at the same time, the MLCP activity of VSMC was significantly increased after hypoxia, with a decrease in MLCK activity. AVP treatment resulted in an increase in MLC20 phosphorylation of SMA and decreased in MLCP activity of VSMC, which could be inhibited by PKC ε isoform inhibitory peptide. AVP and PKC ε isoform inhibitory peptide had no significant influence on MLCK activity. CONCLUSION AVP can restore the decreased vascular reactivity after hemorrhagic shock via PKC ε isoform, and its mechanisms is possibly through inhibiting the activity of MLCP and increasing MLC20 phosphorylation, followed by improves the calcium sensitivity of VSMC and enhances the vascular reactivity.