Tempol selectively attenuates angiotensin II evoked vasoconstrictor responses in spontaneously hypertensive rats.

Objective: To assess whether superoxide anions mediate vasoconstrictor responses to agonists in blood vessels of spontaneously hypertensive rats (SHRs).

Methods: The effect of the superoxide dismutase mimetic, 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol), on responses to angiotensin II (Ang II), endothelin-1, phenylephrine and potassium chloride was determined in aortic rings and perfused mesenteric vascular beds (MVB) of adult male rats of the Sprague-Dawley, Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) strains. The effect of tempol on Ang II-evoked superoxide production was assessed in aortic rings.