Membrane potential and sodium flux in neuroblastoma X glioma hybrid cells: Effects of amiloride and serum

✍ Scribed by Martha E. O'Donnell; Mitchel L. Villereal

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 946 KB
• Volume: 113
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041130308

✦ Synopsis

Abstract

The Na^+^ uptake into neuroblastoma x glioma hybrid cells was measured in Hepes‐buffered EMEM containing 10% calf serum and 5 mM ouabain in the presence and absence of amiloride (1.0 mM). Amiloride was found to markedly inhibit net Na^+^ influx (by approximately 50%). Examination of the effect of amiloride on net Na^+^ influx in the absence of calf serum revealed that a significant amiloride‐sensitive Na^+^ influx remains even under serum‐deprived conditions, although the degree of amiloride inhibition (35%) is substantially lower than that found in the presence of serum. The amiloride‐insensitive portion of Na^+^ influx was found to be independent of serum effects. Estimation of resting membrane potential was made by measurement of the steady state distribution of the lipophilic cation, TPP^+^, in the presence and absence of amiloride. A large, immediate increase in TPP^+^ uptake, indicative of a membrane hyperpolarization, was seen upon addition of amiloride. Determination of the effect of amiloride on resting membrane potential of serum‐deprived cells showed that cells are hyperpolarized to a greater extent in the presence than in the absense of amiloride, and that serum exerts a depolarizing effect on the cells. Thus, serum‐stimulation of Na^+^ influx results in a depolarization of resting membrane potential, while amiloride inhibition of Na^+^ influx causes a hyperpolarization. These data strongly suggest that NG108‐15 cells possess an electrogenic Na^+^ influx pathway that is sensitive to amiloride inhibition and enhanced by serum.