ARTERIAL STRUCTURAL CHANGES IN HYPERTENSIVE RATS INDUCED BY CAPSAICIN AND SALT LOADING
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1. The objective of the present study was to investigate the arterial structural changes in a salt-sensitive hypertensive rat model induced by treatment with capsaicin. 2. Newborn male Wistar rats were treated with 50 mg/kg capsaicin subcutaneously for 2 days. Control rats were treated with vehicle solution (5% ethanol and 5% Tween 80 in saline). After weaning at 3 weeks, rats were divided into four groups: (i) control with a normal salt diet (0.5% NaCl; CON + NS); (ii) control with a high-salt diet (4% NaCl; CON + HS); (iii) capsaicin plus normal salt diet (CAP + NS); and (iv) capsaicin plus a high-salt diet (CAP + HS). Treatment with different salt diets was initiated at 3 weeks of age and lasted for 18 weeks. Tail-cuff systolic blood pressure (BP) and bodyweight were examined. At the end of the treatment period, blood vessels were prepared by perfusion fixation. Heart weight and vascular dimensions were measured in the thoracic (artery) aorta, renal artery and mesenteric artery. 3. Two weeks after the initiation of the salt diet treatment, BP became significantly higher in the CAP + HS group than in any of the other groups and this difference was maintained until the end of the treatment period. 4. Beginning at 8 weeks after the initiation of the salt diet treatment (11 weeks of age), BP became higher in the CON + HS group than in the CON + NS and CAP + NS groups. Blood pressure was not significantly different between the CON + NS and CAP + NS groups. 5. Media thickness, media thickness to lumen ratio and cross-sectional area of the aorta, renal artery and mesenteric artery were significantly increased in the CAP + HS group compared with the other groups. Heart weight was also increased in the CAP + HS and CON + HS groups compared with the other groups. 6. Similar structural changes in the blood vessels and heart were also found in the CON + HS group compared with the CON + NS group. Lumen diameter was not altered by the treatments in any of the arteries studied. 7. We conclude that treatment with capsaicin increased the sensitivity of the BP of these rats to salt and this increase in BP is correlated with hypertrophy of the arteries (vascular remodelling) with no change in lumen size. A long-term high-sodium load induced hypertension in normal Wistar rats, which was accompanied by cardiovascular hypertrophy.