Heightened blood pressure responsiveness to intracarotid infusion of angiotensins in the spontaneously hypertensive rat.

The purpose of this study was to test the hypothesis that intracarotid infusion of angiotensin via a brachial arterial catheter results in a heightened pressor response in the alert spontaneously hypertensive rat (SHR) as previously observed for intracerebroventricular (ICV) injection of angiotensin. We infused angiotensin II and III since these ligands are equivalently potent with respect to peak pressor effect when delivered ICV. We measured somewhat greater pressor responsiveness to AII than to AIII in the Wistar-Kyoto (WKY) normotensive control strain from a baselevel of 133.1 +/- 5.8 (mean +/- SEM) to 151.3 +/- 6.2 mmHg (+13.7%) at the 100 pmol/kg/min dose of AII, and from 132.5 +/- 5.8 to 146.0 +/- 6.1 mmHg (+10.2%) for AIII. The SHR revealed a heightened pressor sensitivity to AII, from a baselevel of 170.0 +/- 3.8 to 200.6 +/- 5.9 mmHg (+18%) while the response to AIII was less dramatic, from 171.3 +/- 2.1 to 189.8 +/- 2.4 mmHg (+10.8%). These findings suggest that a similar heightened pressor responsiveness occurs to peripheral infusion of angiotensin II in the SHR as previously observed to ICV injection.