Effects of mercury and lead on rubidium uptake and efflux in cultured rat astrocytes

Astrocytes readily sequester lead and mercury (8, 10, 19, 22). Accordingly, studies were undertaken to assess the effects of lead and mercury on homeostatic functions in neonatal rat brain primary astrocyte cultures. Both inorganic and organic mercury, but not lead, significantly inhibited the initial rate (5 min) of uptake of ⁸⁶RbCl, used as a tracer for K⁺, at concentrations of 10-100 μM. Mercury and to a lesser extent lead also stimulated the efflux of intracellular ⁸⁶Rb⁺ at 10-500 μM. These observations suggest that the astrocyte plasma membrane may be an important target for lead and mercury, and that relatively low concentrations of these heavy metals should inhibit the ability of astrocytes to maintain a transmembrane K⁺ gradient.