Angiotension receptors subtypes in the rabbit pulmonary artery

Abstract

Angiotensin II is known to be the main effector peptide of the renin-angiotensin system (RAS) and acts on the angiotensin AT1 receptor to mediate the majority of its effects. However, new evidence is emerging that demonstrates the bioactivity of a variety of angiotensin II fragments, e.g. angiotensin IV, des-Asp-angiotensin I (dAAI) and angiotensin-(1-7). This recent discovery has challenged our views on the final effectors and regulation of the RAS and the significance of poly angiotensins both physiologically and pathophysiologically. The role of the bioactive fragments of angiotensin II in regulating the rabbit pulmonary circulation and the possible mechanisms of actions of these peptides were studied in the pulmonary trunk (the vessel arising from the right ventricle prior to its bifurcation into the left and right pulmonary arteries) and pulmonary arteries. The differential responses produced by angiotensin II and its immediate metabolites via two positionally located and functionally opposing receptor subtypes suggest that angiotensin II bioactive fragments play an important role in fine-tuning or regulating angiotensin responses.