Effects of magnesium on cytomorphology and enzyme activities in thyroid of rats.

Till date knowledge regarding the effects of high dietary magnesium on thyroid gland is incomprehensive though certain epidemiological studies reported development of thyroid gland dysfunctions in people with chronic exposure to hard water (especially with high magnesium) despite sufficient iodine consumption. The present study is to explore the effects of chronic high dietary magnesium exposure on thyroid morphology and functional status. Male adult albino Wistar strain rats were treated with graded doses of magnesium sulphate (MgSO4; 0.5, 1.0 and 1.5 g %) for 60 days and changes in different thyroid parameters were investigated. Significantly stimulated thyroid peroxidase and Na+–K+-ATPase and altered idothyronine 5/- deiodinase type I activities, enhanced serum thyroxine (T4) (both total and free), total triiodothyronine (T3) and thyroid stimulating hormone with decreased free T3 levels and T3/T4 ratio (T3:T4) along with enlargement of thyroid with associated histopathological changes were observed in the treated groups. The results clearly confirm that chronic high dietary magnesium exposure causes potential thyroid disruption as reported in earlier epidemiological studies.

Effects of sport fatigue and poverty of movement on neuroendocrine system in Wistar rats / 中国病理生理杂志

AIM: To observe the different changes of neuroendocrine systems between the state of sport fatigue and poverty of movement. METHODS: 60 male Wistar rats were randomly divided into three groups: normal control group, sport fatigue model group and poverty of movement model group (20 rats in each group). The sport fatigue model was established by the method of combining basal diet and loaded swimming during 2 weeks, whereas the method of restricted activities was used to establish the poverty of movement model with total experimental time of 10 weeks. By the end of experiment, the climbing pole time was determined. The contents of hypothalamus thyrotropin releasing hormone (TRH), and serum norepinephrine (NE) and epinephrine (E) in rats with different treatments were determined by ELISA. In addition, the changes of hypothalamus corticotropin release hormone (CRH), pituitary adrenocorticotropic hormone (ACTH) and thyroid stimulating hormone (TSH), and serum corticosterone (CORT), triiodothyronine (T_3), tetraiodothyronine (T_4) were determined by radioimmunoassay to evaluate the functions of adrenergic nerve-adrenomedullin system, hypothalamo-pituitary-adrenal (HPA) axis and hypothalamo-pituitary-thyroid (HPT) axis. RESULTS: Compared to control group, the climbing pole time of the animals was obviously decreased in two model group. The adrenergic nerve-adrenomedullin system and HPA axis were inhibited in sport fatigue model rats, but HPT axis was unchanged. Interestingly, the HPA axis was hyperfunctional and HPT axis was inhibited in poverty of movement model rats. However, no change in the adrenergic nerve-adrenomedullin system was observed. CONCLUSION: Sport fatigue and poverty of movement all affect neuroendocrine system and lead to the adjustment mechanism imbalance, but the target and tendency are different.