Renal vascular adjustments to partial renal venous obstruction in dog kidney.

Blood flow studies were conducted in neurolept anesthetized dogs to characterize the involvement of renal nerves in ipsilateral renal vasoconstriction seen during acute elevation of renal venous pressure above 30 mm Hg. Renal blood flow was measured electromagnetically. The vasoconstrictor response was almost abolished by acute surgical denervation of the kidney, since renal vascular conductance remained unchanged during renal venous pressure elevation from 30-60 mm Hg. However, following additional alpha-adrenoceptor blockade or chronic renal denervation, renal vascular conductance increased progressively during renal venous pressure elevation to 60 mm Hg. The effect of acute decapsulation of kidney was studied in another group of dogs. Decapsulation induced a vasoconstriction. The decrease in renal vascular conductance observed during renal venous pressure elevation was unaffected by acute surgical denervation of decapsulated kidney, but was almost abolished following additional alpha-adrenoceptor blockade or chronic denervation. In decapsulated chronically denervated kidney, the increase in renal vascular conductance during renal venous pressure elevation to 60 mm Hg was still present but considerably attenuated as compared with the chronically denervated kidney with intact capsule. The renin-angiotensin system did not participate in acute vascular adjustments to renal venous stasis in intact kidney or in decapsulated acutely surgically denervated kidney. The data favor the view that neurogenic and myogenic mechanisms significantly influence the vasoconstrictor response to renal venous pressure elevation in dog kidney. The neurogenic contribution to the vasoconstrictor response comprises intrarenal and extrarenal vasoconstrictor mechanisms evoked reflexively by renal venous pressure elevation, and the myogenic contribution to the vasoconstrictor response comprises opposing vasodilator mechanisms due to increase in renal interstitial tissue pressure during renal venous pressure elevation.