Intracoronary Angiotensin II causes inotropic and vascular effects via different paracrine mechanisms Article uri icon

abstract

  • We hypothesized that Angiotensin II (Ang II), like other circulating hormones, acts exclusively intravascularly. To activate or block solely intravascular Ang II receptors, Ang II and its peptide receptor blocker saralasin (Sar) were covalently coupled to a inert polymer (POL, MW >4000 kD) forming Ang II-POL and Sar-POL. These two nonpermeable polymers, Ang II and Sar, were intracoronarily administered into the isolated, saline-perfused rat hearts. Ang II-POL and Ang II caused a dose-dependent ventricular positive inotropic (%2bI) and vasoconstrictor effects (%2bV) which were blocked by Sar. Sar-POL blocked their %2bI but not their %2bV. Thus, Ang II and Ang II-POL act on endothelial luminal receptors through paracrine mechanisms. %2bI were blocked solely by purinoceptor antagonists and paralleled by augmented venous release of ATP degradation products (adenosine, inosine and hypoxanthine). In contrast, %2bV were blocked solely by aspirin, indomethacin or a thromboxane A 2 receptor antagonist. Intracoronary administration of ATP-γ-S and U46169, a purinergic, and TXA2 agonists, respectively, mimicked %2bI and %2bV. The results indicate that ATP is the paracrine inotropic mediator while thromboxane A 2 is the vasoconstrictor mediator. Thus, the %2bI and %2bV distinct effects by intracoronary Ang II indicate that its diverse mechanism of action along the coronary vascular tree may be due to a functionally heterogenous endothelium. © 2004 Published by Elsevier Inc.

publication date

  • 2004-01-01