[Effect of enalaprilat, an angiotensin converting enzyme inhibitor, on the membrane potential of cultured neuroblastoma-glioma hybrid NG108-15 cells].

The effect of enalaprilat on the membrane potential of cultured neuroblastoma-glioma hybrid NG108-15 cells was investigated using the current clamp method. The NG108-15 cell line characteristically differentiates into neurons after addition of 1 mM dibutyryl cAMP to the culture medium. First it was found that enalaprilat inhibits both sodium and calcium currents in the cell membrane of differentiated NG108-15 cells. At concentrations between 10 and 100 microM, this inhibitory effect was reversible and transient, and occurred in a dose-dependent manner. Prolonged washing with normal saline (> 20 min) was needed to completely reverse the inhibitory effect of enalaprilat. The higher the concentration of enalaprilat, the greater its suppressant action on the membrane potential, and at high concentrations (100 microM), enalaprilat caused the peak membrane potential to disappear. When cells were incubated with enalaprilat, 100 microM, for longer periods, however, this inhibitory effect appeared to become irreversible. These findings suggest that enalaprilat has an inhibitory effect on the electrophysiological activity of neurons especially on membrane calcium currents.