Renal Arteriolar Angiotensin Responses During Varied Adenosine Receptor Activation

Abstract We performed experiments to test the hypothesis that endogenous adenosine acts as an essential cofactor re-quired for eliciting angiotensin II (Ang II)-induced afferent and/or efferent arteriolar vasoconstriction. Enalaprilat (2 mg IV) was administered to anesthetized rats to reduce endoge-nous Ang II levels. Kidneys and blood were harvested from these animals and used for study of renal microvascular function using the in vitro blood-perfused juxtamedullary nephron technique. Arteriolar inside diameter was monitored videomicroscopically in (1) normal kidneys, (2) kidneys sub-jected to adenosine receptor blockade (100 ^imol/L 1,3-dipro-pyl-8-p-sulfophenylxanthine), and (3) kidneys continuously exposed to 1 /wnol/L adenosine. Under resting conditions, arteriolar diameters were similar in all three groups of kidneys, averaging 24.8 ±1.0 jun (n=23) in afferent arterioles an