Changes in Antioxidant Status, Protein Concentration, Acetylcholinesterase, (Na+,K+)-, and Mg2+-ATPase Activities in the Brain of Hyper- and Hypothyroid Adult Rats

Abstract

It is a common knowledge that metabolic reactions increase in hyperthyroidism and decrease in hypothyroidism. The aim of this work was to investigate how the metabolic reactions could affect the total antioxidant status (TAS), protein concentration (PC) and the activities of acetylcholinesterase (AChE), (Na+,K+)-ATPase and Mg2+ -ATPase in the brain of hyper- and hypothyroid adult male rats. Hyperthyroidism was induced in rats by subcutaneous administration of thyroxine (25 microg/l00 g body weight) once daily for 14 days, while hypothyroidism was induced by oral administration of propylthiouracil (0.05%) for 21 days. TAS, PC, and enzyme activities were evaluated spectrophotometrically in the homogenated brain of each animal. TAS, PC, and Mg2+ -ATPase activity were found unaffected in hyperthyroidism, while AChE and Na+,K+ -ATPase activities were reduced by 25% (p < 0.01). In contrast, TAS, (Na+,K+)-ATPase and Mg2+-ATPase activities were found to be increased (approx. 23-30%, p < 0.001) in the hypothyroid brain, while AChE activity and PC were shown to be inhibited (approx. 23-30%, p < 0.001). These changes on brain enzyme activities may reflect the different metabolic effects of hyper- and hypothyroidism. Such changes of the enzyme activities may differentially modulate the brain intracellular Mg2+, neural excitability, as well as the uptake and release of biogenic amines.

Changes in acetylcholinesterase, Na+,K+-ATPase, and Mg2+-ATPase activities in the frontal cortex and the hippocampus of hyper- and hypothyroid adult rats

“…In a previous in vivo study from our group, conducted on rat whole-brain tissues [28], we found a statistically significant reduction of AChE and Na + ,K + -ATPase activities in hyperthyroid rats, whereas hypothyroid rats exhibited a reduction in AChE activity and an increase in Na + ,K + -and Mg 2+ -ATPase activities. Moreover, in a recent in vivo study of ours [29] that was conducted on adult rat cerebellar and hypothalamic tissues, neither hyper-nor hypothyroidism had any effect on the examined hypothalamic enzymes, whereas in the cerebellum, both hyper-and hypothyroidism induced a statistically significant decrease in the activities of both AChE and Na + ,K + -ATPase.…”

Resveratrol improved the spatial learning and memory in subclinical hypothyroidism rat induced by hemi-thyroid electrocauterization

“…It has been demonstrated that thyroid dysfunction affected synaptic proteins in adult rats [26]. Thyroid hormone deficiency resulted in the down-regulation of syt-1 expression in rat hippocampus [25,27] and cerebellum [28], and the impairment in hippocampal-dependent tasks of learning and memory [29].…”

The Relationship Between Thyroid States, Oxidative Stress and Cellular Damage

“…There are data indicating that excess thyroid hormones act at multiple levels to cause apoptosis, because this higher level enhances the expression of several death receptors and their ligands, such as TNF-, FasL, proNGF, and proBDNF, resulting in activation of apical caspase-8, which is further amplified through the activation of the p75NRT-mediated pathways (Kumar et al, 2007). Hyperthyroid animals appear to have a shorter lifespan and, at an advanced age, have a myelin deficit (Carageorgiou et al, 2005). It is known that hyperthyroidism increases hepatic protein oxidation, as evidenced by a significant 88% increase in the content of protein hydrazone derivatives 3 days after a T 3 treatment.…”