Biophysical properties of cultured human glial cells

Abstract

Biophysical studies were performed on cultured human fetal brain cells identified by morphologic, cytologic and biochemical characteristics as astrocytic glia. Resting potentials were low (¯X= −7.7mV) because of the temperature during examination and because of an altered intracellular NaK ratio attributed to the culture metabolic conditions. Low resting potential appears unrelated to membrane biophysical properties and does not block the cell's ability to divide and grow although the growth rate is reduced15. The cells displayed no spontaneous electrical activity nor were regenerative responses seen despite large membrane potential displacements. The astrocytic membranes were non-rectifying to imposed current pulses. The glial cell's time constant averaged 311 μsec, 1/26 that of the feline Betz cell35 but less than one standard deviation smaller than that found forin vivo feline astrocytes56. Membrane specific capacitance was found to be about 1 μF/sq.cm, a value common to many biological membranes. Membrane specific resistance averaged 327 ω·sq.cm, a very low value compared to that of neurons but in accord with calculations from other glial (astrocyte) studies. These biophysical values allow rapid transfer of large amounts of potassium.