Objective To perform high-salt hypertension model in SD rats and observe effects and oxidative stress and gender differences in SD rats, and then evaluate mechanism that blood pressure is affected by oxidative stress induced by cold environment.
Methods The male and female SD rats were randomly divided into four groups (n=8): male control group (MC), female control group (FC), male high-salt group (MS), female high-salt group (FS), MC and FC were fed regularly, MS and FS were fed with diet composed of 8% salt. Feeding period was 8 weeks. Four groups were fed regularly in ninth week; in the first 10 weeks, four groups were put into a 4°C artificial climate box in tenth, 1 h per day. Systolic blood pressure (SBP) in SD rats was measured every other day from 1st week to in first 4 days 9th week with tail cuff. Systolic blood pressure in SD rats was measured daily with tail cuff in late 3 days of 9th week and 10th weeks.24-h urine in each group was collected by biological metabolism, calculated accurately.
Results 1. High-salt diet for 8 weeks, MS group and FS group blood pressure was significantly higher than the control group the same sex (p<0.05). In 10th weekend four sets of blood pressure after cold exposure (BP) were higher, MS group and the FS group blood pressure ΔBP (ΔBP=before exposure BP-after exposure BP) significantly higher than the control group the same sex (p<0.01). 2. 8 week FS and MS 24 h urine volume, urinary mALB, urinary RBP, urine sodium, urine potassium excretion higher than that of the same sex control group (p<0.01); MS and FS groups showed no change in exposure;3. After cold exposure high salt group 24 h urinary 8-iso-PGF2α excretion compared with before the cold exposure was significantly higher (p<0.01), serum Ang II levels than before the cold increased and serum NO concentration decreased (p<0.05), while no change in the control group. Before and after cold exposure the MS and FS, MC compared with FC no gender differences emerged. 4. After cold exposure NADPH oxidase activity and SOD activity, MS compared with FS, MC compared with FC does not appear gender differences, but the gender of the high salt group was significantly higher (p<0.05).
Conclusion 1. High-salt diet increased blood pressure, and high-salt diet on blood pressure after high salt gender differences emerged; resume normal diet of high salt hypertensive rats have a certain recovery of renal function, blood pressure, but high salt blood pressure, gender differences still exist in blood pressure. Control group with the same sex, short-term acute cold exposure for high-salt hypertensive rats blood pressure increased significantly; 2. Cold high-salt hypertensive rats after exposure, oxidative stress increased; but male and female rats after exposure to cold and oxidative stress between the gender differences are not shown.