Effect of intermittent hypoxia onthyroid hormone, thyroid ultrastructure and the expression of thyroid Peroxiredoxin5 in rats

Objective To mimic the intermittent hypoxia during sleep of obstructive sleep apnea hypopnea syndrome (OSAHS) in human.We established imtermittenthypoxia (IH) animal model in rats, to investigate the oxidative stress, inflammation reaction, thyroid hormone levels, thyroid ultrastructure and the expression of thyroid Peroxiredoxin5 in rats of intermittent hypoxia. Methods Healthy Sprague-Dawley (SD) rats (16) were randomly divided into 2 groups: the control group and the IH group.The rats in IH group were placed in an animal chamber subjected to imtermittent hypoxia.Circulation to the cabin filled with nitrogen, oxygen and compressed aircycle of 120 s, the minimum oxygen concentration in cabin was to 6%~7%.Experimental design for about 8 hours every day, 7 days a week, for 4 weeks, a total of 28 days.The rats in control group were placed in the same animal chamber at the same time every day and accessed to the same flow of air.After the experiment, we measured the level of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), interleukin 6 (IL-6), tumor necrosis factor-α (TNF-α), free triiodothyroxine (FT3), free thyroxine (FT4), thyroid-stimulation hormonle (TSH) in rats serum, and observed the changes of rat thyroid ultrastructure under electron microscope, and measured Peroxiredoxin5 expression in rat thyroid by immunohistochemistry. Results ①The levels of MDA and IL-6 and TNF-α in rats serum was increased in IH group, and had a significant difference (P<0.05). The levels of SOD and GSH-Px in rats serum was discreased in IH group, and showed significant difference (P<0.05). ②The levels of FT3 in rats serum was increased in IH group, but did not show significant difference (P<0.05). The levels of FT4 and TSH in rats serum was increased in IH group, and showed significant difference (P<0.05). ③Ultrastructure of rat thyroid in IH group: Change of hypoxia overall.④Peroxiredoxin5 positive staining cells mainly located in the cytoplasm of the thyroid.Compared with the control group, Peroxiredoxin5 expression in rat thyroid was higher in IH group, and had a significant difference (P<0.05). Conclusions There are obviously inflammation reactions in rats of intermittent hypoxic.Intermittent hypoxia on the thyroid has a significant stimulating effect, which can directly damage the structure and function of the thyroid, also can increase the level of oxidative stress thyroid, eventually cause thyroid hormone secretion disorders, target organ damage. Key words: Sleep apnea, Obstructive; Cellular hypoxia; Oxidative stress; Thyroid hormone