Chronic lead intoxication affects the myelin membrane status in the central nervous system of adult rats.

The aim of the experiments presented here was to discern whether prolonged consumption of leaden water, which imitates an environmental exposure, affects the structure of myelin in the central nervous system of adult rats and whether the observed morphological destruction is reflected in biophysical and/or biochemical changes. The results indicated that during chronic lead (Pb) intoxication, the Pb level of the myelin fraction increases significantly. Electron microscopy studies show that myelin in control experiments is built up of ordered layers, whereas in a Pb-intoxicated sample, this order is destroyed in large areas of all preparations. Morphological disturbances in Pb-intoxicated in vivo myelin were reflected by changes in myelin membrane fluidity measured by spectrofluorometry and electron paramagnetic resonance (EPR). Prolonged Pb toxicity also caused significant changes in the morphological structure of oligodendrocytes, an increase of phosphatidylethanolamine, and decrease of protein SH group levels. Simultaneously, we found that the protein and total phospholipid content and levels of phosphatidylinositol, sphingomyelin, phosphatidyloserine, cholesterol, and the pattern of total myelin protein obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in Pb-intoxicated myelin did not change compared to control values. Also, Pb intoxication did not induce peroxidation by itself and did not accelerate peroxidation produced by iron (Fe) in brain myelin.