Suppression of Glucocorticoid Response in Stressed Mice Using 50 Hz Electric Field According to Immobilization Degree and Posture

Various studies on immobilized BALB/c mice to evaluate changes in hormone levels associated with stress responses have advanced the characterization of multiple aspects of the biological actions of extremely low-frequency (ELF) electric fields (EFs). In this study, we aimed to investigate the effect of mouse posture on its stress responses and evaluate the importance of adjusting the stress degree in the model. Mice were immobilized inside centrifuge tubes and exposed to an ELF EF generated between parallel plate electrodes. Blood was collected under anesthesia immediately after EF exposure, and plasma glucocorticoids were assayed. The inhibitory effects of EFs on glucocorticoid elevation by immobilization were reproduced regardless whether mice were in the abdominal or lateral recumbent position, for the EF vector delivered to mice through the sagittal or frontal plane. The effect of ELF EF was reproduced in moderately and mildly stressed mice but not in severely immobilized mice. Hence, adjusting the stress degree is critical to the reproducibility of the results for this model. We characterized the effects of ELF EF on homeostasis, including the stress response, and provided valuable information for the scientific evaluation of the biological risks and medical applications of ELF EF.

Stress-Reducing Effect of a 50 Hz Electric Field in Mice after Repeated Immobilizations, Electric Field Shields, and Polarization of the Electrodes

Simple Summary

With the increasing demand for electricity and electrical equipment, humans are routinely and unintentionally exposed to electric fields (EFs). Although no considerable adverse effects of EF exposure have been observed, slight physiological effects are known to occur. Additionally, there are methods and devices that expose subjects to EF for medical purposes. The mechanism of the biological effects of EF has not been identified, because the effects are not strong and may involve the physical properties of EFs, which are invisible and easily disturbed by obstacles. In a simple and short experiment using mice, we found that EF has an inhibitory effect on glucocorticoid (GC) responses. The experiment’s reproducibility was almost 100%. We tried to improve the understanding of the biological effects of EF by structuring our observations of the stress-reducing effects under different conditions in the system. We found that the inhibitory effect on the GC response was attenuated by EF shielding. We compared the effects of EF shielding between the head and abdomen, and found that the effects of EF were attenuated in both conditions, but might be more attenuated when the head was shielded. Thus, it appears that the area where the EF is distributed and the body part are important for the biological effects of EF. Two experiments with different conditions were performed. These results will help advance the current understanding of the effects of EF on stress systems.

Abstract

In BALB/c mice, immobilization-increased plasma glucocorticoid (GC) levels are suppressed by extremely low frequency (ELF) electric fields (EF). The aim of this study was to advance our understanding of the biological effects of ELF-EF, using its suppressive effect on the GC response. Mice were exposed to a 50 Hz EF of 10 kV/m via a parallel plate electrode and immobilized as needed. We examined the suppressive effect of ELF-EF on GC level change after repeated immobilizations, electrode polarization, and EF shielding of different portions of the mouse body parts. Additionally, bodyweight changes owing to stress and EF were examined. Immobilization-induced reduction in the plasma GC levels was reproduced in mice with stress and EF exposure, regardless of the stress episode numbers and electrode polarization. Furthermore, when the head of mice was shielded from the EF, the suppressive effect was possibly relatively lower than that when the abdomen was shielded. The bodyweight of the mice decreased for 3 days after immobilization before recovering; ELF-EF did not affect the bodyweight. Thus, to elicit the biological effects of the EF, not only the size of the area where the EF is distributed but also the area where the field is distributed should be important. The results also confirmed the stableness of the present experimental system, at least in terms of the stress-reducing effect. In addition, the restriction in this study caused weight loss, but ELF-EF was not considered to affect it. The results improve the understanding of the biological effect and medical applications of ELF-EF.

Demonstrative Experiment on the Favorable Effects of Static Electric Field Treatment on Vitamin D3-Induced Hypercalcemia

Simple Summary

Static electric field (SEF) treatment by high-voltage alternating current is a traditional complementary medicine in Japan. Although it is believed that the SEF-induced electric current serves to regulate cellular or humoral responses in patients, the mechanism for SEF treatment remains poorly understood. There have been very few experimental reports on the biological action with SEF treatment. The aim of this study was to elucidate the effects of SEF treatment on vitamin D₃ (Vit D₃)-induced abnormalities in mice. SEF treatment improved the abnormalities in the renal function tests and the imbalance of serum electrolytes. In addition, this treatment remarkably attenuated the Vit D₃-induced tissue injuries (severe tissue calcification in the kidneys, hearts, and stomachs). It was likely that the SEF treatment had some favorable effects on the metabolism of calcium. In conclusion, this study provides important evidence that SEF treatment can reduce hypercalcemia and remove calcium deposits from the renal, cardiac, and gastric tissues. SEF treatment is useful in the regulation of disorders caused by an imbalance of serum electrolytes. This study experimentally demonstrates the favorable effects of SEF treatment on Vit D₃-induced hypercalcemia. For small animals, the larger the body surface area per body weight becomes, the higher the therapeutic efficacy with SEF treatment.

Abstract

The purpose of this study was to elucidate the effects of static electric field (SEF) treatment on vitamin D₃ (Vit D₃)-induced hypercalcemia and renal calcification in mice. The mice were assigned to three groups: Vit D₃-treated mice, mice treated with Vit D₃ and SEF (Vit D₃ + SEF), and untreated mice. After the administration of Vit D₃, the Vit D₃ + SEF-treated mice were exposed to SEF treatment by a high-voltage alternating current over five days. Serum biochemical examinations revealed that both the creatinine and blood urea nitrogen concentrations were significantly higher in the Vit D₃-treated group. Significantly, decreased Cl concentrations, and increased Ca and inorganic phosphorus concentrations, were found in the Vit D₃-treated group. In the Vit D₃ + SEF-treated group, these parameters returned to the levels of the untreated group. In the Vit D₃-treated group, histopathological examinations showed marked multifocal calcification in the lumens of the renal tubules and the renal parenchyma. The myocardium was replaced by abundant granular mineralization (calcification), with degeneration and necrosis of the calcified fibers. The stomach showed calcification of the cardiac mucosa. SEF treatment remarkably attenuated the Vit D₃-induced hypervitaminotic injuries. In conclusion, this study provides important evidence that SEF treatment can reduce hypercalcemia and remove calcium deposits from the renal, cardiac, and gastric tissues. SEF treatment is useful in the regulation of disorders caused by an imbalance of serum electrolytes.

Effects of Exposure to a 50Hz Electric Field on Plasma Levels of Lactate, Glucose, Free Fatty Acids, Triglycerides and Creatine Phosphokinase Activity in Hind-Limb Ischemic Rats

We previously reported that extremely low frequency electric fields (ELF-EFs) affect energy metabolism in stressed conditions. To further confirm this, the effect of exposure to ELF-EFs on the experimental ischemic rat was examined. The test was based on a comparison of rats treated with EF alone, ischemic surgery alone, the combination of EF with ischemic surgery, or no treatment (double sham). The EF condition used in this study was an alternating current of 50 Hz EF at 17 500 V/m intensity for 15 min per day. The exposure to EF in ischemic rats significantly decreased plasma levels of free fatty acids and triglycerides, compared to those of the no treatment or EF alone group. The plasma lactate levels of two ischemic groups peaked on experimental day-4 and gradually decreased until the end of the study. The changes in the lactate levels induced by ischemia did not show any difference between rats treated with ischemia alone or a combination of ischemia with an EF. Any changes in plasma levels of glucose and creatine phosphokinase activity were not influenced by EF treatment. These results indicate that the EF effect on glycolysis parameters, plasma lactate or glucose levels, does not appear in a highly stressed condition and that EF effects varied dependent on the condition of organism but ELF-EF used in this study have impact on lipid metabolism parameter in a hind-limb ischemic rat. However, further studies are needed to elucidate the association of ELF-EF with the lipid metabolism system.