Enhanced Contractility of Renal Afferent Arterioles From Angiotensin-Infused Rabbits

Abstract

We tested the hypothesis that cyclooxygenase (COX), thromboxane A₂ synthase (TxA₂-S), thromboxane prostanoid receptors (TP-Rs), or superoxide anion (O₂⁻) mediates enhanced contractions of renal afferent arterioles (Aff) of angiotensin II (Ang II)-infused rabbits. Rabbits were infused with vehicle (sham), Ang II 60 ng·kg⁻¹·min⁻¹ (Ang II 60) or 200 ng·kg⁻¹·min⁻¹ (Ang II 200). There was a selective enhanced vasoconstriction of Affs from Ang II 60 rabbits to Ang II (Δdiameter−78±8% versus −43±9%; PPP−1 activating TP-Rs, whereas enhanced responses in rabbits infused with a lower Ang II dose are dependent on TP-R but not O₂⁻.