Impact of intermittent hypoxic exposure on estrous cycle in female rats

Abstract

Objective To investigate the effect of intermittent hypoxic exposure on estrous cycle in female rats. Methods Healthy female SD rats were randomized after 5 d of adaptive feeding into normal control group maintained in routine conditions and hypoxic exposure group with daily hypoxic exposure simulating the condition at an altitude of 6 000 m for 8 h in a hypobaric chamber (n=11). During the 4 weeks of exposure, the rats were allowed free access to standard laboratory chow and sterile water. The food intake of the rats was recorded daily and their body weight twice a week. The organ /body weight ratios were used to assess the effects of hypoxic exposure on the vital organ coefficients. The morphological changes of vaginal exfoliated cells were examined twice a day to assess the changes of the estrous cycle. After the exposure, aortic blood samples were collected from all the rats to determine the serum levels of sex hormones and malondialdehyde(MDA) and the activities of superoxide dismutase(SOD) and glutathione peroxidase(GSH-Px). Results Compared with the normal control group, the rats within 7 d of hypoxic exposure showed significantly decreased food intake, and significant decrease in body weight occurred within 10 d of the exposure. Hypoxic exposure significantly increased the organ coefficients of the kidney, liver and spleen but did not significantly affect the uterus and ovaries of the female rats. Morphological analysis of the exfoliated cells showed that hypoxic exposure significantly prolonged the estrus and metestrus phase and shortened the diestrus period of the rats. Hypoxic exposure resulted in significantly decreased serum levels of progesterone and luteinizing hormone, lowered the activities of GSH-Px and SOD and increased MDA content as compared with those in the control group. Conclusion Hypoxic exposure can cause estrous cycle disorder in female rats possibly by inducing oxidative stress.

Keywords

• hypoixa
• estrous cycle
• oxidative stress