Neurotoxicity in rats chronically exposed to lead ingestion: measurement of intracellular concentrations of free calcium and lead ions in resting or depolarized brain slices.

The intracellular free calcium (Ca2+) or lead (Pbi2+) ions were measured by using 19F-NMR and 1,2-bis(2-amino-5-fluorophenoxy)ethane-N,N,N',N'-tetraacetic acid in brain slices obtained from control rats and rats chronically exposed to 1 mg/kg.day or 100 mg/kg.day dose of Pb acetate ingestion. The basal Cai2+ values obtained in this study were comparable to the values reported previously for brain neurons by using the Fura-2 method (Singh, 1993a). The concentrations of total Pb in blood samples obtained from 2-week old rats exposed to 1 and 100 mg/kg.day doses of lead acetate were 31 and 521 micrograms/dl respectively. The concentrations of total Pb in brain samples obtained from 2-week old rats exposed to 1 and 100 mg/kg.day doses of lead acetate were 150 and 2700 ng/g respectively. The concentration of Pb in neonatal and adult samples did not differ significantly. Free Pb2+ was not detected in samples obtained from the rats exposed to a Pb dose of 1 mg/kg.day; however, a small concentration (ranging from 100 to 300 pM) of the ion was detected in samples obtained from the rats exposed to a Pb dose of 100 mg/kg.day. This suggests that either a small proportion of total Pb is ionized in brain or there is an efflux of Pb2+ from intracellular fluid into the incubation medium. Depolarization caused significant increase in Cai2+ in cortical slices obtained both from control and Pb-exposed rats. However, depolarization increased Pbi2+ only in samples obtained from rats exposed to a Pb dose of 100 mg/kg.day.(ABSTRACT TRUNCATED AT 250 WORDS)