Intrarenal injection of radiocontrast medium (RCM) results in transient vasoconstriction and a persistent decline in glomerular filtration rate (GFR). Adenosine modulates this vasoconstrictor response and is postulated to increase oxygen free radical (OFR) generation. We hypothesized that the persistent decline in (GFR that follows RCM administration results in an increased generation of OFR. We evaluated the effects of RCM injection on renal blood flow, inulin clearance, hypoxanthine, xanthine, and malondialdehyde concentrations in four groups of non-volume-expanded, pentobarbital sodium anesthetized dogs in the presence and absence of intravenous allopurinol, 25 mg/min (group 1), intrarenal superoxide dismutase (SOD), 400 U/min (group 2), heat-inactivated intrarenal SOD, 400 U/min (group 3), and simultaneous infusions of intrarenal SOD, 400 U/min, to one kidney and saline to the other (group 4). Both allopurinol and SOD significantly attenuated the fall in GFR after RCM administration over control. Malondialdehyde concentrations were attenuated over control in all treated groups, indicating a decrease in OFR generation. We conclude that intrarenal injection of RCM results in increased production of OFR. Inhibition of OFR production by allopurinol and increased OFR removal by SOD attenuates the effects of RCM on declines in GFR.

Endothelin, a newly discovered endothelial-derived peptide, has been demonstrated in vitro to have potent vasocontractile properties and has been speculated to play a role in vivo in arterial pressure-volume homeostasis. The present studies in anesthetized dogs were designed to determine the action of endothelin on cardiovascular-renal and endocrine function in vivo as in acute arterial pressure-volume regulation. Intravenous infusion of endothelin (50 ng/kg per min) increases arterial pressure by increasing peripheral vascular resistance but in association with an increase in coronary vascular resistance and decreases in cardiac output. Renal blood flow and glomerular filtration rate were markedly reduced in association with a sustained reduction in sodium excretion and an increase in plasma renin activity. Atrial natriuretic factor, vasopressin, and aldosterone were also elevated. These results indicate that endothelin is a potent vasoconstrictor that elevates systemic blood pressure in association with marked decreases in cardiovascular and renal function. This peptide may function as a counterregulatory hormone to the effects of endothelial-derived vasodilator agent(s).

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The current study demonstrates that significant ventricular dysfunction with peripheral vasoconstriction can be associated with normal renal function and thus suggests an important functional role for the neurohumoral profile of ALVD in preserving sodium balance.

Abstract-Endothelin-1 (ET-1) is a cardiovascular peptide that binds to two distinct receptors, ET A and ET B , resulting in systemic and regional vasoconstriction, alteration in sodium excretion, mitogenesis, and release of other vasoactive peptides such as atrial natriuretic peptide (ANP). A role for ET-1 has been proposed in congestive heart failure (CHF) based on the increase in circulating ET-1 in this cardiovascular disease state. The present study determined the cardiorenal and endocrine responses to chronic selective oral ET A antagonism in experimental CHF. Two groups of conscious dogs underwent 21 days of pacing-induced CHF. These groups included a control untreated group (nϭ6) and a group that received an orally active ET A receptor antagonist (A-127722, Abbott Pharmaceuticals, 5mg/kg PO bid, nϭ6). Each group was studied at baseline before the onset of CHF and after 14 and 21 days of CHF. Compared with the CHF control group, the ET A receptor antagonism group at 14 days of CHF showed lower mean arterial pressure and systemic vascular resistance. Similarly, ET A receptor antagonism markedly attenuated the increase in circulating ANP despite similar atrial pressures. At 21 days of CHF, ET A receptor antagonism lowered pulmonary artery pressure, pulmonary vascular resistance, and systemic vascular resistance in association with a higher cardiac output. Plasma ANP remained suppressed. Despite the lower mean arterial pressure and circulating ANP in the ET A receptor antagonist group, the absolute decrease in sodium excretion from baseline was less compared with the untreated CHF control group. The present investigation supports the conclusion that endogenous ET-1 participates in the systemic and pulmonary vasoconstriction, the elevation of ANP, and the sodium retention that characterize this model of experimental CHF, suggesting a potential therapeutic role for ET A receptor antagonism in CHF. (Hypertension. 1998;31:766-770.)