EFFECTS OF LEAD AND MERCURY ON HISTAMINE UPTAKE BY GLIAL AND ENDOTHELIAL-CELLS

The effects of lead and mercury on [H-3]-histamine uptake by cultured astroglial and endothelial cells of rat brain were studied. Experiment al data showed that both metal ions inhibited the uptake in both cell types of concentrations as low as 1-10 mu M. The effects were consiste nt with non/competitive inhibitions. With either lead or mercury expos ure, the inhibition of the uptake was greater in astroglial than in ce rebral endothelial cells. Contrary to the above findings, 100 mu M of mercuric chloride produced stimulation of histamine uptake and this st imulation was much more pronounced in cultured cerebral endothelial ce lls than in astroglial cells. Inhibition of [H-3]-histamine uptake by lead acetate and mercuric chloride was considered to be association wi th a loss of the transmembrane Na+ and/or K+ gradient while stimulatio n of the uptake by high concentration of mercury might be related to a direct effect on histamine transporter. It is noteworthy, that cultur ed astroglial cells, derived from neonatal rat brain, are much more se nsitive to the toxic effects of these heavy metal ions than cultured e ndothelial cells derived from the brain capillaries of the same specie s of animals.