Effects of hypomagnetic field on hormone and blood indexes in laboratory rodents

Geomagnetic field (GMF) is a key environmental factor for all living organisms on Earth. Geomagnetic field has been implicated as an important factor for orientation and navigation in many kinds of animals. However, the disruption of geomagnetic field would cause a variety of biological responses. For example, daily repeated magnetic field shielding induced analgesia in mice. In this study, we aimed to investigate the effects of continuous long-term hypomagnetic field (HMF) exposure on hormone and blood indexes in C57BL/6 mice and in SD rat. Results showed that the contents of thyroxine (T4) in mice decreased significantly at the 3rd, 6th, 12th week (P < 0.05). However, other testing indexes showed significant difference in a single week exposure, no continuous differences. The number of white blood cells (WBC) of mice increased significantly at the 1st week. However, the levels of hormones in rats had shown significant continuous decrease since 2-week. After returned to the geomagnetic field, the contents of hormone in rats rose to the levels in normal geomagnetic field. The number of WBC of rats in HMF group had significantly increased (P<0.05) after the 3-week exposure. These results showed that the responses to hypomagnetic field exposure for mice and rats were not consistent. It might be due to the species difference. This study indicated that T4 and WBC might be physiological indexes sensitive to the hypomagnetic field exposure in laboratory rodents, which should be paid special attention to in future studies.