Effects of angiotensin-(1-7) and angiotensin II on vascular tone in human cirrhotic splanchnic vessels.

Abstract

Evidence suggests that the renin angiotensin system (RAS) may play a role in the pathological splanchnic vasodilatation that leads to a hyperdynamic circulation in cirrhosis. An impaired contractile response to the angiotensin II peptide of the classical RAS system has been described in animal models of cirrhosis and in vivo in cirrhotic subjects. Furthermore, in experimental cirrhosis, the so-called alternate arm of the RAS was found to be upregulated and its effector peptide, angiotensin-(1-7) was shown to attenuate splanchnic vascular tone. The aim of this study was to explore the relevance of these findings to human disease. Omental arteries from cirrhotic and controls subjects were studied in isolation using a wire myograph. Varied protocols to evaluate the vasoactivity of RAS mediators were enacted. The contractile response to angiotensin II was comparable in cirrhotic vs control splanchnic arteries (61 ± 9 vs 68 ± 11% KPSS, respectively). Despite this, however, arterial contractility of the cirrhotic vessels correlated negatively with Child Pugh score (p = 0.0003, r=-0.83) and there was evidence that angiotensin II-induced contractility was increased in early cirrhosis. Angiotensin II-induced contractility was attenuated by angiotensin-(1-7) in cirrhotic and control arteries, however, adrenergic responses were not affected by angiotensin-(1-7). Contractile responses to angiotensin II are preserved in narrow lumen human cirrhotic splanchnic arteries and are comparatively augmented in early disease. Angiotensin-(1-7) had no vasodilatory effect on adrenergic tone, however, attenuated angiotensin II-induced contractility, possibly through an Ang-(1-7)-AT1R interaction, and thus may contribute to pathological vasodilatation in human cirrhosis.