VOLTAGE-DEPENDENT MEMBRANE CURRENTS OF CULTURED HUMAN NEUROFIBROMATOSIS TYPE-2 SCHWANN-CELLS

Previous experimental observations indicate that inhibition of voltage -dependent K+ currents suppresses proliferation of normal Schwann cell s. In the present study we tested the opposite relationship, i.e., whe ther Schwann cells from tumors with abnormally high rates of prolifera tion would have an increase in membrane K+ currents. Whole-cell membra ne currents were studied in cultured cells from schwannomas of two neu rofibromatosis type 2 (NF2) patients (n = 53), one patient with a spor adic schwannoma (n = 22), and two control subjects (n = 41). Five diff erent types of voltage-dependent membrane currents were found in all o f the Schwann cells tested. Membrane depolarization activated outward K+ and Cl- currents; quinidine was found to block the K+ current (IC50 approximate to I mu M), and NPPB reduced the Cl- current. Ba2+-sensit ive inward rectifier K+ currents, fast Na+ currents, and a transient, inactivating K+ current were less frequently observed. On average, NF2 cells were found to have statistically significant higher membrane po tential and larger non-inactivating K+ outward current as compared to controls. Electrophysiological parameters of Schwann cells from a spor adic schwannoma showed a tendency for larger outward currents; however , the difference did not reach statistical significance. Together the data support the suggestion of a possible link between K+ outward curr ent and proliferation of Schwann cells. (C) 1998 Wiley-Liss, Inc.