Moderate intrarenal vasoconstriction after high pressor doses of norepinephrine in the rat: comparison with effects of angiotensin II.

AIMS Treatment of arterial hypotension with norepinephrine (NE) is associated with renal vasoconstriction and may lead to ischemic kidney injury; the risk involved is still a matter of debate. METHODS In anesthetized, acutely uninephrectomized rats, we examined changes in intrarenal hemodynamics induced by intravenous infusion of NE and angiotensin II (Ang II), at doses that increased arterial pressure by ∼25 mm Hg (20%). Renal blood flow (RBF) was determined using a Transonic probe, and superficial cortical, outer and inner medullary flows (CBF, OMBF, IMBF) as laser-Doppler fluxes. RESULTS NE decreased regional intrarenal perfusion similarly, by 16, 15 and 16% for RBF, OMBF and IMBF, respectively (all changes significant). The respective decreases after Ang II were significantly greater and clearly differentiated: 45, 32 and 22%, respectively. The renal vascular resistance increased 47 ± 4% after NE and 131 ± 11% after Ang II, indicating that the latter drug induces much more pronounced renal vasoconstriction. CONCLUSION An ∼15% decrease of renal perfusion may be taken as an indication of an impairment of renal circulation during antihypotensive NE therapy. While superiority of NE over Ang II is obvious, a further search for drugs even less harmful to renal perfusion and function is desirable.