Electron probe microanalysis of isolated brain capillaries poisoned with lead

The blood-brain barrier has been proposed as an important site for the toxic action of lead in the central nervous system. To investigate this, capillary endothelial cells were isolated from rat cortex and exposed to lead in vitro. Tissue suspensions were then prepared for electron microscopy and X-ray microprobe analysis. In cells exposed in vitro to lead, electron-dense deposits were observed within mitochondria. With X-ray analysis, it was determined that these intramitochondrial deposits contained lead in a non-crystalline matrix. Also, lead appeared to be accumulated in the same intramitochondrial areas as calcium. The results suggest that lead is preferentially sequestered in mitochondria of capillary endothelial cells. Further, this selective localization may be associated with lead-induced disruptions in intracellular calcium metabolism and transepithelial transport processes.