Nerve Growth Factor influences potassium movements in chick embryo dorsal root ganglionic cells

Abstract

Recently we have shown that Nerve Growth Factor (NGF) influences the movement of Na + across the membrane of chick embryo dorsal root ganglion (DRG) cells. When cell dissociates from 8-day embryonic chick DRG, equilibrated with 86Rb + (a K + analog) in the presence of NGF, were transferred to NGF-free medium a marked loss of intracellular K + occurred over several hours. The time course of K + loss was similar to the time course of Na + accumulation which occurs in the absence of NGF. NGF-deprived, K +-depleted DRG cells reaccumulated K + within minutes of delayed NGF presentation, just as delayed NGF administration results in the rapid extrusion of Na + from Na +-loaded cells. Restoration of K + competence was dependent upon NGF concentration. The occurrence of this K + response to exogenous NGF in other ganglionic preparations correlated with traditional responses to NGF in culture and previously observed Na + responses. Neither the development nor the expression of the ionic defect (K + depletion, Na + filling) during NGF deprivation required the presence of both cations in the medium. NGF-dependent restoration of intracellular K + in NGF-deprived chick DRG cells required the presence of intracellular Na +, and NGF-dependent extrusion of Na + required extracellular K +. Thus NGF appears to influence the coupled (active) movements of Na + and K + across the membrane of its target cells, possibly by means of the classical Na +, K +-ATPase pump.