THE ROLE OF VOLTAGE-GATED CA2-LOW-FREQUENCY (ELF) MAGNETIC-FIELD STIMULATION( CHANNELS IN NEURITE GROWTH OF CULTURED CHROMAFFIN CELLS INDUCED BY EXTREMELY)

The ion Ca2+ has been shown to play an important role in a wide variet y of cellular functions, one of them being related to cell differentia tion in which nerve growth factor (NGF) is involved. Chromaffin cells obtained from adrenals of 2- to 3-day-old rats were cultured for 7 day s. During this time, these cells were subjected to the application of either NGF or extremely low frequency magnetic fields (ELF MF). Since this induced cell differentiation toward neuronal-like cells, the mech anism by which this occurred was studied. When the L-Ca2+ channel bloc ker nifedipine was applied simultaneously with ELF MF, this differenti ation did not take place, but it did when an N-Ca2+ channel blocker wa s used, In contrast, none of the Ca2+ channel blockers prevented diffe rentiation in the presence of NGF. In addition, Bay K-8644, an L-Ca2channel agonist, increased both the percentage of differentiated cells and neurite length in the presence of ELF MF. This effect was much we aker in the presence of NGF. [H-3]-noradrenaline release was reduced b y nifedipine, suggesting an important role for L-Ca2+ channels in neur otransmitter release. Total high voltage Ca2+ currents were significan tly increased in ELF MF-treated cells with NGF, but these currents in ELF MF-treated cells were more sensitive to nifedipine. Amperometric a nalysis of catecholamine release revealed that the KCl-induced activit y of cells stimulated to differentiate by ELF MF is highly sensitive t o L-type Ca2+ channel blockers. A possible mechanism to explain the wa y in which the application of magnetic fields can induce differentatio n of chromaffin cells into neuronal-like cells is proposed.