INFLUENCE OF ELECTROMAGNETIC-FIELDS ON BONE MASS AND GROWTH IN DEVELOPING RATS - A MORPHOMETRIC, DENSITOMETRIC, AND HISTOMORPHOMETRIC STUDY

The effect of electromagnetic fields on bone is debated. In an experim ental study of this effect, we compared two lots of growing female rat es (both lots n = 15, age 3 weeks, average weight 23.2 +/- 3.3 g), one of which was exposed to a 3-mT, 100-Hz, Helmholtz-type electromagneti c field for 24 hours a day for 30 days, and the other of which served as the control. Bone development and bone mass were evaluated by morph ometry, densitometry, and histomorphometry. The rats were killed at 30 days and weighed. The right femurs were dissected, measured, and weig hed; bone densitometry was used to determine femoral bone mineral cont ent (BMC) and density (BMD), and histomorphometry of the nondecalcifie d bone was used to determine trabecular bone volume (Cn-BV-TV%), numbe r (Tb-N mm) and thickness (Tb-Th mu m), intertrabecular space (Tb-Sp m u m) and growth cartilage thickness (Gc-Th mu m). Ln the rats exposed to the electromagnetic field, BMC and BMD (P = 0.019 and P = 0.002, re spectively) and Cn-BV-TV, Tb-N, Tb-Th (P = 0.005, P = 0.036, and P = 0 .027, respectively) all were decreased, whereas Tb-Sp was increased (P = 0.002). There were no significant differences in initial and final body weight, or in final femur weight, femur length, and GC-Th. These findings indicate that electromagnetic fields of the type used here re duced bone formation and increased bone resorption without affecting b one development in rats.