Background B is a well known cause of neurotoxicity, but our understanding of the mechanisms underlying toxicity is incomplete. No information was available on the subcellular localization of B in vivo. Materials/methods Young SPRD rats (100-200g) were anesthetized and 50 mg/kg B (containing 200μCi [3H]B) was infused iv over 5 min. Rats were sacrificed at 10 (n=7) and 30 (n=8) min after the start of the infusion, and the brain vasculature was flushed in situ with ice-cold saline. Brains were homogenized in 0.32M sucrose using a glass-Teflon homogenizer, followed by subcellular fractionation in sucrose gradients. Fractions were removed in aliquots of 2 mL, and the protein content of each fraction was determined. 10 mL of scintillation cocktail was added to each fraction for scintillation counting. Serum B concentration was determined in serum obtained immediately prior to sacrifice, and the specific activity of B was determined for each rat by scintillation counting of duplicate 10 μL serum samples. Data from the subcellular fractions were contrasted using nonparametric analysis of variance.FigureResults Serum B concentrations were 529±78 and 349±42 μmol/L (mean± SD) at 10 and 30 min respectively. There were significant differences between B concentrations in subcellular fractions at both time points (KW=35.8, p<0.0001 at 10 min [see figure]. KW=43.2. p<0.0001 at 30 min [not shown]). The distribution between fractions did not change over time (data not shown). Conclusion In the presence of an intact blood-brain barrier B entering the brain appears to achieve the highest concentrations in membranes and cytoplasm of brain cells. Although this does not prove that the basic mechanism of B neurotoxicity is necessarily associated with these fractions. knowing the concentrations of B associated with the different subcellular compartments may be of value in designing and evaluating studies of the effects of B on basic cellular functions.

figure 1

Figure 1