Characteristics of lead adaptation in a rat kidney cell line. I. Uptake and subcellular and subnuclear distribution of lead.

Two sublines of normal rat kidney cell (NRK 52-E) that are resistant to 5 and 10 microM lead nitrate have been developed and characterized. The cellular and nuclear uptake of 210Pb, as well as the subnuclear distribution, was unchanged by lead adaptation: it remained at values of 2.3-6.6 pmole 210Pb/microgram protein/h. Also no difference in the slope of the curve of the uptake rate of the three cell types could be detected. Studies of the nuclear uptake of 210Pb showed that in both normal and lead-adapted cells the major lead fraction was associated with the chromatin and mostly (63-67%) with the nuclear proteins. Electron microscopic studies demonstrated that particulate lead was taken up in all lead-exposed cells. It was concluded that development of resistance to lead does not arise from a reduced rate of cellular uptake, from increased excretion, or from changes in nuclear uptake or in the subnuclear distribution within the cells.