Cholesterol induces renal vasoconstriction and anti-natriuresis by inhibiting nitric oxide production in anesthetized rats

Abstract

Although hypercholesterolemia is implicated in the pathophysiology of many renal disorders as well as hypertension, its direct actions in the kidney are not yet clearly understood. In the present study, we evaluated renal responses to administration of cholesterol (8 microg x min(-1).100 g body wt(-1); bound by polyethylene glycol) into the renal artery of anesthetized male Sprague-Dawley rats. Total renal blood flow (RBF) was measured by a Transonic flow probe, and glomerular filtration rate (GFR) was determined by Inulin clearance. In control rats (n = 8), cholesterol induced reductions of 10 +/- 2% in RBF [baseline (b) 7.6 +/- 0.3 microg x min(-1).100 g(-1)], 17 +/- 3% in urine flow (b, 10.6 +/- 0.9 microg x min(-1).100 g(-1)), 29 +/- 3% in sodium excretion (b, 0.96 +/- 0.05 mumol.min(-1).100 g(-1)) and 24 +/- 2% in nitrite/nitrate excretion (b, 0.22 +/- 0.01 nmol.min(-1).100 g(-1)) without an appreciable change in GFR (b, 0.87 +/- 0.03 ml.min(-1).100 g(-1)). These renal vasoconstrictor and anti-natriuretic responses to cholesterol were absent in rats pretreated with nitric oxide (NO) synthase inhibitor, nitro-l-arginine methylester (0.5 microg x min(-1).100 g(-1); n = 6). In rats pretreated with superoxide (O(2)(-)) scavenger tempol (50 microg x min(-1).100 g(-1); n = 6), the cholesterol-induced renal responses remained mostly unchanged, although there was a slight attenuation in anti-natriuretic response. This anti-natriuretic response to cholesterol was abolished in furosemide-pretreated rats (0.3 microg x min(-1).100 g(-1); n = 6) but remained unchanged in amiloride-pretreated rats (0.2 microg x min(-1).100 g(-1); n = 5), indicating that Na(+)/K(+)/2Cl(-) cotransport is the dominant mediator of this effect. These data demonstrate that cholesterol-induced acute renal vasoconstrictor and antinatriuretic responses are mediated by a decrease in NO production. These data also indicate that tubular effect of cholesterol on sodium reabsorption is mediated by the furosemide sensitive Na(+)/K(+)/2Cl(-) cotransporter.

Fig. 1.

Infusion of PEG-cholesterol increase renal membrane cholesterol content. Content of cholesterol in the kidney in vehicle-infused group (n = 6) and cholesterol-infused group (n = 7). Data normalized to total protein content. *Significant difference vs. vehicle-infused group (P < 0.05).

Fig. 2.

A: renal vascular resistance (RVR) responses in percent changes to intra-arterial infusion of cholesterol in vehicle pretreated group (●; n = 8), l-NAME pretreated group (△; n = 6), and tempol pretreated group (□; n = 6). B: RVR responses in percent changes to intra-arterial infusion of cholesterol in amiloride pretreated group (◊; n = 5) and furosemide pretreated group (▿; n = 6). *Significant difference vs. pretreatment values (P < 0.05).

Fig. 3.

A: renal blood flow (RBF) responses in percent changes to intra-arterial infusion of cholesterol in vehicle pretreated group (●; n = 8), l-NAME pretreated group (△; n = 6), and tempol pretreated group (□; n = 6). B: RBF responses in percent changes to intra-arterial infusion of cholesterol in amiloride pretreated group (◊; n = 5) and furosemide pretreated group (▿; n = 6). *Significant difference vs. pretreatment values (P < 0.05).

Fig. 4.

A: glomerular filtration rate (GFR) responses in percent changes to intra-arterial infusion of cholesterol in vehicle pretreated group (●; n = 8), l-NAME pretreated group (△; n = 6), and tempol pretreated group (□; n = 6). B: GFR responses in percent changes to intra-arterial infusion of cholesterol in amiloride pretreated group (◊; n = 5) and furosemide pretreated group (▿; n = 6). There were no appreciable changes in all groups.

Fig. 5.

A: urine flow (V) responses in percent changes to intra-arterial infusion of cholesterol in vehicle pretreated group (●; n = 8), l-NAME pretreated group (△; n = 6), tempol pretreated group (□; n = 6). B: V responses in percent changes to intra-arterial infusion of cholesterol in amiloride pretreated group (◊; n = 5) and furosemide pretreated group (▿; n = 6). *Significant difference vs. pretreatment values (P < 0.05).

Fig. 6.

A: absolute sodium excretion (U_NaV) responses in percent changes to intra-arterial infusion of cholesterol in vehicle pretreated group (●; n = 8), l-NAME pretreated group (△; n = 6), and tempol pretreated group (□; n = 6). B: U_NaV responses in percent changes to intra-arterial infusion of cholesterol in amiloride pretreated group (◊; n = 5) and furosemide pretreated group (▿; n = 6). *Significant difference vs. pretreatment values (P < 0.05). ^#Significant difference vs. response in vehicle pretreated group (P < 0.05).

Fig. 7.

A: fractional sodium excretion (FE_Na) responses in percent changes to intra-arterial infusion of cholesterol in vehicle pretreated group (●; n = 8), l-NAME pretreated group (△; n = 6), and tempol pretreated group (□; n = 6). B: FE_Na responses in percent changes to intra-arterial infusion of cholesterol in amiloride pretreated group (◊; n = 5) and furosemide pretreated group (▿; n = 6). *Significant difference vs. pretreatment values (P < 0.05). #Significant difference vs. response in vehicle pretreated group (P < 0.05).

Fig. 8.

A: urinary nitrite/nitrate excretion (U_NOxV) responses in percent changes to intra-arterial infusion of cholesterol in vehicle pretreated group (●; n = 8), l-NAME pretreated group (△; n = 6), and tempol pretreated group (□; n = 6). B: U_NOxV responses in percent changes to intra-arterial infusion of cholesterol in amiloride pretreated group (◊; n = 5) and furosemide pretreated group (▿; n = 6). *Significant difference vs. pretreatment values (P < 0.05).