Nerve growth factor action on 2-deoxy-D-glucose transport in dorsal root ganglionic dissociates from chick embryo

Dorsal root ganglionic cells, when incubated in vitro in the absence of nerve growth factor (NGF), undergo a general metabolic degeneration which is preceded by loss of certain permeation properties. To determine in which ways an absence of NGF can also affect the capacity of these cells to take up an important energy source, namely glucose, experiments were carried out in which cells were incubated with or without NGF for varying times, and then presented with the factor and tested for the ability to take up 3H-labeled 2-deoxy-D-glucose. As with exogenous uridine, hexose transport in DRG cells was reduced by NGF deprivation and restored by delayed NGF administration (up to 6 h). Both the initial rate and equilibrium level were affected in an NGF dose-dependent fashion. Calculation of apparent Kt and V max in NGF-deprived and NGF-supported cells showed about two-fold differences between NGF-controlled and NGF-independent hexose transports, suggesting corresponding differences between NGF-dependent and other ganglionic cells. Restoration of hexose transport by delayed NGF administration took place within minutes of presentation of the factor. The delay before onset of restoration and the speed with which restoration was achieved have been found also to be dependent on the NGF concentration, suggesting that they reflect equilibration kinetics between NGF and its binding sites rather then the development of the response within cells. Thus, NGF can rapidly modulate permeation properties which regulate the availability of major energy substrates for the cell. This effect of NGF is discussed in the content of current views on the mode of action of the factor.