RESUMO
To study the effect of chronic exposure to native high altitude [HA] on blood pressure, and to investigate the underlying mechanism of action. This study was carried out between February and April 2011. A total of 20 male rats were divided into 2 groups [n=10 rats]. The low altitude [LA] group were rats born and lived in an LA environment at King Saud University, College of Pharmacy, Riyadh, Kingdom of Saudi Arabia [KSA], and the HA group were rats born in the same LA area, then acclimatized to HA area in Physiology Department, King Khalid University, College of Medicine, Abha, KSA for 90 days. At the end of day 90, hematocrit, plasma renin activity, aldosterone, norepinephrine and vasopressin levels were determined in both groups. Invasive arterial blood pressure was also measured, and fractional excretion of sodium [FENa], and potassium [FE[K]] were calculated. The quantitative real time-polymerase chain reaction of renin was carried out in the kidneys of both rat groups. When compared to LA native rats, HA rats exhibited a significant increase in systolic and diastolic blood pressure with a significant increase in renin plasma activity as well as an increase in the levels of aldosterone, norepinephrine, and vasopressin. Furthermore, HA rats showed a significant increase in renin expression in their kidneys, as well as decreased FENa. Data shows that prolonged exposure to HA results in elevated blood pressure precipitated by the activation of the renin-angiotensin-aldosterone system
RESUMO
To evaluate the effect of high altitude on markers of thyroid function, serum lipid profile and tissues oxidative stress in male Wistar rats native to high altitude [HA] with male rats native to low altitude [LA]. Randomized experimental animal study. Physiology laboratory, Medical School of King Khalid University. Male rats aged six months, weighing 250 gm were bred and maintained at low altitude [LA, 600 m above sea level, n=6] or high altitude [HA, 2800 m, n=6], under the same laboratory conditions and fed the same diet. Blood samples were obtained for thyroid hormones and lipid profile analysis. Livers, kidneys, lungs and testes were collected and used for determination levels of thiobarbituric acid reactive substances [TBARS], reduced glutathione [GSH], Superoxide Dismutase [SOD] and Catalase Activity [CAT]. HA rats had significantly [P<0.05] lower serum T3 [17.14%], T4 [13.75%], TSH [39.29%] and total cholesterol [15.84%] and LDL [60.90%].There were no significant differences in TAG or HDL. All tissues from HA rats showed significant decreases in SOD and CAT activities compared to LA rats. These rats showed significantly higher oxidative stress in the lungs and the liver, but lower oxidative stress in the kidney and no difference in the testes. Living at high altitude environment results in impaired thyroid function and lipid metabolism and causes increased tissue oxidative stress