Objective-The study was undertaken to assess whether the changes in urinary excretion of eicosanoids (a decrease of 6-keto-PGF,, and PGF, and an increase of thromboxane) previously found in lead (Pb) exposed workers may decrease the renal haemodynamic response to an acute oral protein load. Methods-The renal haemodynamic response was estimated by determining the capacity of the kidney to increase the glomerular filtration rate (in terms of creatinine clearance) after an acute consumption of cooked red meat (400 g). A cross sectional study was carried out in 76 male Pb workers (age range 30 to 60 years) and 68 controls matched for age, sex, socioeconomic state, general environment (residence), and workshift characteristics.
With the help of urinary markers, nephron segment-specific effects of chronic low-level Pb exposure could be detected in children. The pattern of effects on glomerular, proximal and distal tubular and interstitial markers was similar to that previously observed in adults. The changes, however, occur at lower b-Pb levels than in adults. The current threshold appears to be justified also from a nephrological point of view, and children can indeed be considered a special risk group.
A controversy presently exists concerning the ability of albumin to inhibit the tubular reabsorption of low-molecular-weight (Mr) proteins in experimental renal diseases leading to massive proteinuria. We have examined the urinary excretion of albumin and of 2 low-Mr proteins, β2-microglobulin and cystatin C, in rats treated with toxins affecting primarily the glomerulus (puromycin aminonucleoside and Adriamycin) or the tubule (mercuric chloride and maleic acid). Above a threshold of 100 mg/24 h, albuminuria induced by puromycin aminonucleoside (50 mg/kg) and Adriamycin (5 mg/kg) was associated with a marked increase in the urinary excretion of β2-microglobulin and cystatin C peaking at more than 100-fold the baseline levels. These glomerulotoxins did not affect the urinary excretion of the tubular enzyme N-acetyl-β-D-glucosaminidase. This pattern of effects was completely different from that induced by mercuric chloride (2 mg/kg) and maleic acid (400 mg/kg) which increased the excretion of both N-acetyl-β-D-glucosaminidase and low-Mr proteins in rats with albuminuria values below 100 mg/24 h. These results strongly support the hypothesis that at high filtered loads, albumin decreases the tubular uptake of low-Mr proteins most likely by competition for a common transport mechanism.
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