Sodium intake but not renal nerves attenuates renal venous pressure-induced changes in renal hemodynamics in rats.

Abstract

Increased central venous pressure and renal venous pressure (RVP) are associated with worsening of renal function in acute exacerbation of congestive heart failure. We tested whether an acute isolated elevation of RVP in one kidney leads to ipsilateral renal vasoconstriction and decreased glomerular filtration rate (GFR) and whether this depends on dietary salt intake or activation of renal nerves. Male Lewis rats received a normal (1% NaCl, NS) or high-salt (6% NaCl) diet for ≥14 days before the acute experiment. Rats were then randomized into the following three groups: time control and RVP elevation to either 10 or 20 mmHg to assess heart rate, renal blood flow (RBF), and GFR. To increase RVP, the left renal vein was partially occluded for 120 min. To determine the role of renal nerves, surgical denervation was conducted in rats on both diets. Renal sympathetic nerve activity (RSNA) was additionally recorded in a separate group of rats. Increasing RVP to 20 mmHg decreased ipsilateral RBF (7.5 ± 0.4 to 4.1 ± 0.7 ml/min, P < 0.001), renal vascular conductance (0.082 ± 0.006 to 0.060 ± 0.011 ml·min-1·mmHg-1, P < 0.05), and GFR (1.28 ± 0.08 to 0.40 ± 0.13 ml/min, P < 0.05) in NS rats. The reduction was abolished by high-salt diet but not by renal denervation. Furthermore, a major increase of RVP (1.6 ± 0.8 to 24.7 ± 1.2 mmHg) immediately suppressed RSNA and decreased heart rate ( P < 0.05), which points to suppression of both local and systemic sympathetic activity. Taken together, acute elevated RVP induces renal vasoconstriction and decreased GFR, which is more likely to be mediated via the renin-angiotensin system than via renal nerves.