Modulatory effects of quercetin on hypobaric hypoxic rats.

Quercetin is an active constituent of Hippophae rhamnoides L. and Ginkgo Biloba, which are commonly taken for high altitude sickness. The preventive effect of quercetin on hypobaric hypoxic rats was investigated. Male Wistar rats (180-220 g) were placed into six groups: normoxic group (normal control), a hypoxic group (model control), three quercetin-treated groups (5, 10, 20mg/kg, i.g.), and acetazolamide-treated group (22.5mg/kg, i.g., positive control), 10 animals in each group. Hypoxic rats were raised in a hypobaric hypoxia chamber simulating a high altitude of 5000 m for 23 h per day after a five-day pretreatment. Normoxic control rats were raised at an altitude of 300 m. After the five-day treatment, hemodynamic, arterial blood gas and electrolyte parameters, antioxidants and nitric oxide metabolism were measured. Hypobaric hypoxia enhanced the right ventricular systolic pressure, right ventricular end-diastolic pressure and left ventricular end-diastolic pressure, which were reversed by quercetin. Quercetin increased the declined pH, PO(2), Sp(O2), PCO(2) levels in arterial blood induced by hypobaric hypoxia, and increased Na(+), HCO(3)(-), Cl(-), but decreased K(+) concentrations. Quercetin increased superoxide dismutase, catalase, glutathione peroxidase activities, glutathione levels, and it decreased malondialdehyde levels in serum. Furthermore, quercetin increased nitric oxide levels and inducible nitric oxide synthase activity in serum. Rats failed to gain body weight under hypobaric hypoxia and quercetin had no effect on it. These results suggest that the activities of quercetin on cardiac function, arterial blood gas, antioxidants and nitric oxide metabolism may be related to its protective potential on hypobaric hypoxia-induced damage.