Effects of a 4.7 T static magnetic field on fetal development in ICR mice.

In order to determine the effects of a 4.7 T static magnetic field (SMF) on fetal development in mice, we evaluated fetal teratogenesis and endochondral ossification following exposure in utero. Pregnant ICR mice were exposed to a 4.7 T SMF from day 7.5 to 9.5 of gestation in a whole-body dose, and sacrificed on day 18.5 of gestation. We examined the incidence of prenatal death, external malformations and fetal skeletal malformations. There were no significant differences observed in the incidence of prenatal death and/or malformations between SMF-exposed mice and control mice. Further, we evaluated the immunoreactivity for the vascular endothelial growth factor (VEGF), which is implicated in angiogenesis and osteogenesis, in the sternum of fetal mice following magnetic exposure. Our studies also indicated that on day 16.5 of gestation following SMF exposure, the immunoreactivity for VEGF was increased compared to unexposed controls. However, it was decreased in the exposed group compared to the control group on day 18.5 of gestation. DNA and proteoglycan (PG) synthesis were also measured in rabbit costal growth plate chondrocytes in vitro. No significant differences were observed in DNA synthesis between the SMF exposed chondrocytes and the control chondrocytes; however, PG synthesis in SMF exposed chondrocytes increased compared to the controls. Based on these results, we suggest that while SMF exposure promoted the endochondral ossification of chondrocytes, it did not induce any harmful effects on fetal development in ICR mice.