Effects of lead intoxication on intercellular junctions and biochemical alterations of the renal proximal tubule cells.

Lead intoxication is a worldwide health problem which frequently affects the kidney. In this work, we studied the effects of chronic lead intoxication (500 ppm of Pb in drinking water during seven months) on the structure, function and biochemical properties of rat proximal tubule cells. Lead-exposed animals showed increased lead concentration in kidney, reduction of calcium and amino acids uptake, oxidative damage and glucosuria, proteinuria, hematuria and reduced urinary pH. These biochemical and physiological alterations were related to striking morphological modifications in the structure of tubule epithelial cells and in the morphology of their mitochondria, nuclei, lysosomes, basal and apical membranes. Interestingly, in addition to the nuclei, inclusion bodies were found in the cytoplasm and in mitochondria. The epithelial cell structure modifications included an early loss of the apical microvillae, followed by a decrement of the luminal space and the respective apposition and proximity of apical membranes, resulting in the formation of atypical intercellular contacts and adhesion structures. Similar but less marked alterations were observed in subacute lead intoxication as well. Our work contributes in the understanding of the physiopathology of lead intoxication on the structure of renal tubular epithelial cell-cell contacts in vivo.

Vitamin-E reduces the oxidative damage on delta-aminolevulinic dehydratase induced by lead intoxication in rat erythrocytes.

Lead intoxication induces oxidative damage on lipids and proteins. In the present paper we study in vivo and in vitro the antioxidant effect of vitamin-E and trolox, on the oxidative effects of lead intoxication in rat erythrocytes. Vitamin-E simultaneously administered to erythrocytes treated with lead was capable to prevent the inhibition of delta-aminolevulinic dehydratase activity and lipid oxidation. Partial but important protective effects were found when vitamin-E was administered either after or before lead exposure in rats. In vitro, the antioxidant trolox protected delta-ALA-D activity against damage induced by lead or menadione. These results indicate that vitamin-E could be useful in order to protect membrane-lipids and, notably, to prevent protein oxidation produced by lead intoxication.

[Trans-membrane potential in Entamoeba]. / Potencial transmembranal en Entamoeba.

The membrane potential in Entamoeba is an important driving force for the uptake of substrates. In Entamoeba invadens PZ a membrane potential of -36 mV was obtained when Nernst equation was applied to the distribution at equilibrium of 86Rb+ in the presence of valinomycin. This could explain the levels of accumulation of up to 4 times found for positively charged substrates. Membrane potential was diminished by depolarizing conditions (high external K+ concentration in the presence of valinomycin). Moreover, we recorded continuously the membrane potential of Entamoeba invadens PZ and Entamoeba histolytica HM1 using the fluorescent lipophilic cation diisopropylthiodicarbocyanine. It was found that the uptake of this cation by the amoebae was fast in both species, conditions that modify the membrane potential (hyperpolarization and depolarization) produced changes in the fluorescence of the dye in agreement with its reported capability to detect variations in membrane potential. It can be concluded that these microorganisms have a membrane potential negative inside them.