Alterations in signal transduction in vascular smooth muscle cells may contribute to vascular hyporeactivity in cirrhosis. Protein kinase C plays a role in vascular cell contraction by modifying contractile proteins and intracellular [Ca2+] homeostasis. The aim of this study was to examine the vascular reactivity and expression of protein kinase Cα in aortae from rats with cirrhosis.Methods:
The contractile response to phorbol ester, a protein kinase C activator, was evaluated in endothelium-denuded aortic rings from normal and cirrhotic rats. Protein kinase Cα expression was determined by Western blot analysis.Results:
Maximal contraction was significantly less marked in cirrhotic(1.24±0.24 g) than in control (3.43±0.27 g) aortae. Phorbol myristate-acetate-induced contraction was dependent on extracellular[Ca2+] concentrations, as shown by a reduction in maximal contraction when control and cirrhotic aortic rings were exposed to a Ca2+-free medium. Increasing the intracellular [Ca2+], by incubation with a Ca2+ ionophore, significantly increased the maximal contraction induced by phorbol myristate-acetate in cirrhotic but not in control rat aortae. Protein kinase Cα expression was significantly lower in aortae in cirrhotic than in control rats.Conclusion:
These results confirm alterations in protein kinase C in aortae from cirrhotic rats.