Abstract
Weak electromagnetic fields (WEF) alter Ca2+ handling in skeletal muscle myotubes. Owing to the involvement of Ca2+ in muscle development, we investigated whether WEF affects fusion of myoblasts in culture. Rat primary myoblast cultures were exposed to WEF (1.75 µT, 16 Hz) for up to six days. Under control conditions, cell fusion and creatine kinase (CK) activity increased in parallel and peaked at 4–6 days. WEF enhanced the extent of fusion after one and two days (by ~40%) vs. control, but not thereafter. Exposure to WEF also enhanced CK activity after two days (almost four-fold), but not afterwards. Incorporation of 3H-thymidine into DNA was enhanced by one-day exposure to WEF (~40%), indicating increased cell replication. Using the potentiometric fluorescent dye di-8-ANEPPS, we found that exposure of cells to 150 mM KCl resulted in depolarization of the cell membrane. However, prior exposure of cells to WEF for one day followed by addition of KCl resulted in hyperpolarization of the cell membrane. Acute exposure of cells to WEF also resulted in hyperpolarization of the cell membrane. Twenty-four hour incubation of myoblasts with gambogic acid, an inhibitor of the inward rectifying K+ channel 2.1 (Kir2.1), did not affect cell fusion, WEF-mediated acceleration of fusion or hyperpolarization. These data demonstrate that WEF accelerates fusion of myoblasts, resulting in myotube formation. The WEF effect is associated with hyperpolarization but WEF does not appear to mediate its effects on fusion by activating Kir2.1 channels.
Highlights
Living organisms are continuously exposed to weak electromagnetic fields (WEF)that can result in multiple biological consequences
We showed that WEF inhibits action potential and hypoxia-mediated increases in intracellular Ca2+ concentration ([Ca2+ ]i ) and protects against muscle damage induced by hypoxia in rat primary skeletal muscle cultures [6]
Hyperpolarization has been implicated in myoblast fusion [13,14], membrane we investigated whether
Summary
That can result in multiple biological consequences. For example, WEF can alter Ca2+. Ca2+ influx is indispensable for fusion and that, at least in human myoblasts, this occurs via T-type Ca2+ channels that open subsequent to membrane hyperpolarization [14]. In view of our earlier findings that WEF altered Ca2+ handling [6], it appeared likely that muscle. Whether WEF affects muscle development, is not known. In view of our earlier findings that WEF altered Ca2+ handling [6], it appeared likely that muscle growth would be affected by WEF. We examined the effects of WEF on fusion of skeletal muscle myoblasts in culture. The results demonstrate that WEF accelerthe fusion of skeletal muscle myoblasts in culture. WEF ates myoblast fusion,fusion, resulting in myotube formation.
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