Effects of aortic stenosis on renal renin, angiotensin receptor, endothelin and NOS gene expression in rats

Renin, endothelial NO synthase and endothelin gene expression in the 2kidney-1clip Goldblatt model of long-term renovascular hypertension

Objective

Numerous reports have shown the influence of renin, nitric oxide (NO) and the endothelin (ET) systems for regulation of blood pressure and renal function. Furthermore, interactions between these peptides have been reported. Aim of our study was to investigate the relative contribution of these compounds in long-term renovascular hypertension/renal ischemia.

Methods

Hypertension/left-sided renal ischemia was induced using the 2K1C-Goldblatt rat model. Renal renin, ET-1, ET-3 and endothelial NO synthase (eNOS) gene expression was measured by means of RNAse protection assay at different timepoints up to 10 weeks after induction of renal artery stenosis.

Results

Plasma renin activity and renal renin gene expression in the left kidney were increased in the clipped animals while eNOS expression was unchanged. Furthermore, an increase in ET-1 expression and a decrease of ET-3 expression was detected in early stenosis.

Conclusions

While renin is obviously involved in regulation of blood pressure and renal function in unilateral renal artery stenosis, ET-1, ET-3 and endothelium derived NO do not appear to play an important role in renal adaptation processes in long-term renal artery stenosis, although ET-1 and ET-3 might be involved in short-term adaptation processes.

Big endothelin-1 is not a predictor in aortic stenosis, but is related to arterial blood pressure

BACKGROUND

In aortic stenosis, natriuretic peptides have recently been shown to correlate with ventricular function and to predict symptom-free survival and outcome. Elevated big endothelin-1 (bigET) is associated with poor prognosis in chronic heart failure, but little is known about its role in severe aortic stenosis.

METHODS

In 61 patients with aortic stenosis (71+/-10 years, mean gradient 65+/-20 mm Hg, valve area 0.63+/-0.15 cm2), plasma bigET was determined by radioimmunoassay and related to echocardiographic parameters, symptoms and survival. Patients were followed for 1 year.

RESULTS

BigET (mean 2.3+/-1.5, range 0.1-7.5 fmol/ml) was elevated > or = 1.9 fmol/ml in 54% of patients, but was not correlated to the transvalvular gradients or valve area. BigET did not differ significantly between 14 asymptomatic (2.4+/-1.0 fmol/ml) and 47 symptomatic patients (2.3+/-1.6 fmol/ml), although the highest levels were observed in 5 patients in NYHA class III-IV (4.2+/-2.2 fmol/ml, p=0.035). No significant difference in bigET was observed between 51 survivors and 10 patients who died during follow-up (2.2+/-1.4 vs 2.7+/-1.6 fmol/ml). BigET did not differ between 7 asymptomatic patients developing symptoms and those remaining asymptomatic during follow-up. BigET was significantly related to the systolic blood pressure and left ventricular systolic pressure (r=0.389, p=0.0025 and r=0.401, p=0.0018, respectively), but not to the diastolic blood pressure or interventricular septal wall thickness. BigET was inversely related to the left ventricular ejection fraction (r=0.327, p=0.01) and fractional shortening (r=0.391, p=0.044).

CONCLUSION

Although frequently elevated, bigET-1 is not a useful predictor of symptoms or outcome in patients with severe aortic stenosis. BigET increases inversely with left ventricular function and directly with systolic left ventricular and blood pressure, but is not related to transvalvular gradients or valve area.

Expression of endothelial nitric oxide synthase is suppressed in the renal vasculature of angiotensinogen-gene knockout mice

We have attempted to elucidate the mechanism by which endothelial-type nitric oxide synthase (eNOS) is regulated in the kidney, with special reference to the role of renal hemodynamics and angiotensin II (Ang II). We compared angiotensinogen gene knockout (Atg-/-) mice, which lacked Ang II (resulting in sodium/water depletion and severe hypotension), with wild-type (Atg+/+) mice. Using Western blot analysis and the NADPH diaphorase histochemical reaction, we found that the expression and activity of eNOS were markedly lower in the renal vessels of Atg-/- mice compared with wild-type (Atg+/+) mice. Dietary salt loading significantly enhanced renal eNOS levels and increased blood pressure in Atg-/- mice, but severe hypotension almost abolished the effects of salt loading. In contrast, in Atg+/+ mice, altered salt intake or hydralazine had no effect on renal eNOS levels. These results suggest that perfusion pressure plays an essential role in maintaining renal vascular eNOS activity, whereas Ang II plays a supportive role, especially when renal circulation is impaired.