Effects Of Oxidative Stress And Gender Differences In SD Rats With High-salt Hypertension Via Acute Short-term Cold Exposure

[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] 16 male and 16 female SD rats, weighing 250-300g, were randomly divided into 4 groups (n = 8): 1. Male control group (MC) was fed regularly; 2. Female control group (FC) was fed regularly; 3. Male high-salt group (MS) was fed with diet composed of 8% salt; 4. Female high-salt group (FS) was fed with diet composed of 8% salt. Feeding period was 8 weeks. Four groups were fed with diet composed of 8% salt in ninth week; in the first 10 weeks, four groups were put into a 4℃artificial climate box in tenth, 1 hour per day.Blood Pressure: blood pressure was measured 1 week before experiment. Systolic blood pressure (SBP) in SD rats was measured every other day in first 4 days from 1st week to 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. Blood pressure was measured 3 times and means value obtained.Urine: 24-hour urine in each group was collected by biological metabolism, calculated accurately, put into a 5ml centrifuge tube and then preserved at -20℃fridge at the end of 8th, 9th and 10th week.1ml vein blood of tail in SD rats was collected by the end of 9th week. Blood serum from carotid artery and thoracic aorta were obtained in SD rats under anesthesia by the end of 10th week. All specimens were preserved in liquid nitrogen and quantization of tissue protein was measured.[Resμlts]1.SBP:Compared with control group, blood pressure in MS and FS increased significantly after 8 weeks(P<0.05). blood pressure in 4 groups increased after cold exposure. Compared with MC,△BP(△BP = BP post-exposure- BP pre-exposure) in MS was high significantly(P<0.05). Compared with FC,△BP in FS was high significantly(P<0.01).2. 24 h urine mALB,RBP,Na + and K +:Compared with control group, 24 hours urines measure , urine mALB , urine RBP , urine sodium and urine potassium discharge rate increased significantly in MS group and FS group at the end of 8 week. Compared with pre cold exposure, 24 hours urines measure , urine mALB , urine RBP , urine sodium and urine potassium discharge rate increased significantly in MS group and FS group at the end of 8 week. Compared with post cold exposure, 24 hours urines measure, urine mALB , urine RBP , urine sodium and urine potassium discharge rate did not change significantly in MS group and FS group at the end of 8 week. Gender differences had no statistically difference at the end of 8 week and pre and post cold exposure.3. 24 hours urinary 8-iso-PGF2α:Compared with pre cold exposure, excretion of 24 hours urine 8-iso-PGF2αin post cold exposure increased significantly (P <0.01). Excretion of 24 hours urine 8-iso-PGF2αin control groups pre and post cold exposure was no significant differences. Excretion of 24 hours urine 8-iso-PGF2αin MS and FS,MC and FC, pre and post cold exposure was no significant differences.4. Serum concentrations of AngII and NO:Compared with pre cold exposure, serum concentrations of AngII in high-salt groups post cold exposure increased and serum concentrations of NO in high-salt groups post cold exposure decreased (P <0.05) and was statistically no differences in control group post cold exposure. Compared with pre cold exposure, serum concentrations of AngII and NO in FS and MS, FC and MC, post cold exposure was statistically no differences.5. Thoracic aortic NADPH oxidase activity and total superoxide dismutase (SOD) activity:After cold exposure the male high salt group compared with the female high salt group, male control group compared with the female control group, no significant difference occurred (P> 0.05), but the high salt group compared with the control exposure NADPH oxidase activity and SOD activity in male and female group significantly higher (P <0.05). [Conclusions]1. high-salt diet led to increase of blood pressure, which lies in gender differences. Blood pressure decrease and renal function in SD rats with high-salt hypertension improve after common diet, but there are gender differences in rats with high-salt hypertension.2. Compared with same gender control group, blood pressure induced by acute short-term cold exposure in rats with high-salt hypertension increase significantly.3. NADPH oxidize is activated, SOD activity decreased, oxygen free radicals increased, oxidative stress enhanced, and then NO was consumed drastically and bioavailability of NO decreased, blood pressure increased in high-salt hypertensive rats after cold exposure,4. Oxidative stress has no differences between genders after cold exposure.