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.