Effects of alacepril and amlodipine on the renal injury induced by a high-cholesterol diet in rats

Effects of allopurinol, a xanthine oxidase inhibitor, on renal injury in hypercholesterolemia‐induced hypertensive rats

To investigate if increased lipid peroxidation is involved in hypercholesterolemia-induced hypertension and renal injury, we examined the effects of allopurinol, a xanthine oxidase inhibitor, on these conditions. Groups of male Sprague--Dawley rats were fed for 8 weeks with a high-cholesterol diet (4% cholesterol), a high-cholesterol plus allopurinol (10 mg/kgBW/day) diet or a normal diet. Systolic blood pressure (SBP), serum lipids, uric acid (UA) and malondialdehyde (MDA) as a measure of lipid peroxides, and urinary excretion of protein (UP) were measured after 0, 4 and 8 weeks. Urinary excretion of nitrite plus nitrate (UNOx) and iron (UFe), and MDA in the kidney were measured after 8 weeks. The renal injury was evaluated by the glomerular sclerosis score (SS). The high-cholesterol diet increased SBP, serum total cholesterol and UA, MDA in the serum and kidney, UP, UNOx, UFe and SS. Allopurinol ameliorated cholesterol-induced elevation in serum UA, MDA in the serum and kidney, UP, UNOx, UFe and SS, but did not affect SBP. Hence, our results suggest that lipid peroxidation may be involved in hypercholesterolemia-induced renal injury, and that suppression of lipid peroxidation can reduce such injury.

Effects of acute hypercholesterolemia on blood pressure and pressor response to norepinephrine in rats

To examine if high cholesterol in blood acutely affects the blood pressure, we partly exchanged the blood of normal rats for that of hypercholesterolemic rats. Male Sprague-Dawley rats were fed for 8 weeks with a high-cholesterol diet (4% cholesterol; HC) or a normal diet (NC). The rats were catheterized; and blood of animals in NC was partly exchanged with that of HC (N-H) or other animals in NC (N-N). Systolic blood pressure (SBP) and the pressor response to norepinephrine (NE) in N-H were compared with those of N-N. Serum lipids and malondialdehyde (MDA), and urinary excretion of protein (UP) and NE (UNE) were determined. After 8 weeks, SBP, serum total cholesterol (TC), MDA, UP and UNE were higher in the HC. Blood exchange caused an increase in TC, MDA and SBP in only the N-H. Increases in SBP caused by NE injection were rather less in the N-H than in the N-N. The blood pressure increase induced by a high-cholesterol diet seemed to be caused by certain factors in the blood of hypercholesterolemic rats. Excessive lipid oxidation induced by hypercholesterolemia may be involved in the blood pressure elevation.

Causes and consequences of increased sympathetic activity in renal disease

Much evidence indicates increased sympathetic nervous activity (SNA) in renal disease. Renal ischemia is probably a primary event leading to increased SNA. Increased SNA often occurs in association with hypertension. However, the deleterious effect of increased SNA on the diseased kidney is not only caused by hypertension. Another characteristic of renal disease is unbalanced nitric oxide (NO) and angiotensin (Ang) activity. Increased SNA in renal disease may be sustained because a state of NO-Ang II unbalance is also present in the hypothalamus. Very few studies have directly compared the efficacy of adrenergic blockade with other renoprotective measures. Third-generation beta-blockers seem to have more protective effects than traditional beta-blockers, possibly via stimulation of NO release. Although it has been extensively documented that muscle SNA is increased in chronic renal failure, data on renal SNA and cardiac SNA are not available for these patients before end-stage renal disease. It is also unknown whether additional treatment with third-generation beta-blockers can delay the progression of renal injury and prevent cardiac injury in chronic renal failure more efficiently than conventional treatment with angiotensin-converting enzyme inhibitors only.