Renoprotective effects of tolvaptan in hypertensive heart failure rats depend on renal decongestion

The vasopressin type 2 receptor antagonist tolvaptan may have renoprotective effects in patients with heart failure (HF). This study aimed to reveal the renoprotective effect of tolvaptan from the viewpoint of hemodynamic combined with catheter and ultrasound examinations in a hypertensive HF model. Dahl salt-sensitive rats (n=24) were fed an 8% high-salt diet after the age of 6 weeks and were treated with tolvaptan (n=16) or vehicle (control group; n=8). The tolvaptan-treated rats were divided into two groups: a low-dose group (0.01% tolvaptan diet; Low-Tol) and a high-dose group (0.05% tolvaptan diet; High-Tol). At 24 weeks, catheterizations to measure central venous pressure (CVP) and renal medullary pressure (RMP) were performed, followed by intrarenal Doppler (IRD) studies and contrast-enhanced ultrasonography (CEUS) to evaluate renal medullary perfusion. The tolvaptan diet reduced CVP (7.7 ± 1.5, 9.0 ± 1.1, and 12.2 ± 0.8mmHg in the High-Tol, Low- Tol, and control groups, respectively; p < 0.001) and RMP (7.7 ± 0.8, 9.4 ± 1.3, and 13.7 ± 1.2mmHg in the High-Tol, Low- Tol, and control groups, respectively; p < 0.001). Tolvaptan also reduced the venous impedance index (VII) in the IRD analysis (0.18 ± 0.03, 0.26 ± 0.04, and 0.40 ± 0.08 in the High-Tol, Low-Tol, and control groups, respectively; p < 0.001), and the time to peak intensity in CEUS (6.0 ± 0.5, 7.3 ± 1.3, 9.8 ± 1.8 s in the High-Tol, Low-Tol, and control groups, respectively; p < 0.001). Creatinine clearance (Ccr) was preserved in both the High-Tol and Low-Tol groups compared to the control group (4.80 ± 1.9, 4.24 ± 0.8, and 1.35 ± 0.3 mg/min, respectively; p=0.001). Ccr was negatively correlated with RMP (R=−0.76, P < 0.001), the venous impedance index (R=−0.70, p < 0.001), time to peak intensity (R=−0.75, P < 0.001), and renal fibrosis (R=−0.70, p < 0.001). In contrast, Ccr had modest correlations with systolic blood pressure (R=−0.50, P=0.02) and left ventricular ejection fraction (R=0.48, P=0.03). This study revealed that the renoprotective effects of tolvaptan in a hypertensive HF model depended on renal decongestion.