The effect of in vitro and in vivo lead intoxication on monosaccharide transport in isolated rat brain microvessels

Abstract

The effect of lead on facilitated transport of monosaccharides into isolated brain microvessels was investigated. Preparations from control rats and from rats exposed to lead acetate at various doses (0.025–1.0 mg lead/g body wt/day) from days 5–25 postnatally were studied. The time courses of uptake for various concentrations of 3-O-methylglucose (3OMG) were determined. Values of 0.6 min and 2.0 min for 5 and 50 mM 3OMG, respectively, were obtained in the case of preparations from control animals. In contrast, the half-time of uptake was about 1 min for both sugar concentrations for microvessels isolated from animals treated at 1.0 mg lead/g body wt/day. This indicates both a block in facilitated transport of the sugar, as well as damage to the endothelial cells resulting in increased passive permeability. There was a dose-response relationship for the effect of in vivo lead treatment on 3OMG transport in isolated microvessels. Microvessel preparations from younger animals (treated at 1.0 mg/g body wt for two days prior to sacrifice at 7 days postnatally) were more sensitive to lead treatment than preparations from adults; equivalent lead burden induced a greater increase in passive permeability to 3OMG in the younger animals. In other experiments microvessels isolated from untreated rats were preincubated with lead acetate. A concentration of 0.1 μM lead acetate in vitro abolished facilitated transport of 3OMG.