Diet-induced hypertension in rats is associated with increased renal vasoconstrictor response to angiotensin II after...

The mechanisms behind development of diet-induced hypertension remain unclear. The kidneys play a paramount role in blood volume and blood pressure regulation. Increases in renal vascular resistance lead to increased mean arterial blood pressure (MAP) due to reduced glomerular filtration rate and Na⁺ excretion. Renal vascular resistance may be increased by several factors, e.g. sympathetic output, increased activity in the renin-angiotensin system or endothelial dysfunction. We examined if a 14-week diet rich in fat, fructose or both led to increased renal vascular resistance and blood pressure. Sixty male Sprague-Dawley rats received normal chow (Control), high-fat chow (High Fat), high-fructose in drinking water (High Fructose), or a combination of high-fat and high-fructose diet (High Fat + Fruc) for 14 weeks from age 4-weeks. Measurements included body weight (BW), telemetry blood pressures, renal blood flow in anesthetized rats, plasma concentrations of atrial natriuretic peptide and glucose, as well as vessel myography in renal segmental arteries. Body weight increased in both groups receiving high fat, whereas MAP increased only in the High Fat + Fruc group. Renal blood flow did not differ between groups showing that renal vascular resistance was not increased by the diets. After inhibiting nitric oxide and prostacyclin production, renal blood flow reductions to Angiotensin II infusions were exaggerated in the groups receiving high fructose. MAP correlated positively with heart rate in all rats tested. Our data suggest that diet-induced hypertension is not caused by an increase in renal vascular resistance. The pathophysiological mechanisms may include altered signaling in the renin-angiotensin system and increases in central sympathetic output in combination with reduced baroreceptor sensitivity leading to increased renal vasoconstrictor responses.