RESUMO
OBJECTIVE: Investigations were carried out to understand the effect of 50 Hz power frequency magnetic field on microfilament assembly of human amniotic cells and on expression of actin and epidermal growth factor receptor. METHODS: Human amnion FL cells were exposed to 0.1, 0.2, 0.3, 0.4, 0.5 mT power frequency magnetic field for 30 minutes. Microfilaments were marked using Phalloidin-TRITC, and then were observed under a fluorescence microscope. An optical method was used to detect the relative content of microfilament in cells. A scanning electron microscope was used to detect the cell shape. The content of actin and epidermal growth factor receptor in the preparation of the detergent-insoluble cytoskeleton were measured by western-blotting to analyse the potential mechanism of the change induced by magnetic field. RESULTS: Intracellular stress fibers were found to decrease after exposing cells to a 0.2 mT power frequency magnetic field for 30 minutes. New microfilament and filopodia bundles appeared at the cell periphery after exposure, but the detected total F-actin content per cell was not significantly changed, detected by a F-actin-specific dye. The change in the amount of microfilaments caused by the field could be recovered 2 hours later when the field was withdrawn. The mean height of microfilament cytoskeleton decreased from (12.37 +/- 1.28) microm to (9.97 +/- 0.38) microm (t = 6.96, P > 0.05) after exposure using a confocal microscope. The cell shapes became more flat and lamellipodia appeared after exposure observed by a scanning electron microscope. By using Western blotting method, the intracellular contents of epidermal growth factor receptor and of actin in the preparation of the detergent-insoluble cytoskeleton which are associated with high-affinity epidermal growth factor receptors, increased about (31.2 +/- 4.1)% (t = 17.10, P < 0.05) and (16.8 +/- 2.3)% (t = 16.68, P < 0.05) respectively, compared with that of the control. CONCLUSION: These results suggest that a short time exposure to a 0.2 mT power frequency magnetic field induces re-organization of microfilament in human amnion FL cells. These changes could be recovered by field withdraw and may have something with the clustering of epidermal growth factor receptors induced by magnetic field.
