Evaluation of selenium exposure in copper refinery workers.

Concentrations of selenium in plasma and urine and activity of glutathione peroxidase in erythrocytes were determined in workers exposed to selenium and in a control group. Plasma selenium concentrations were significantly lower in exposed workers compared to the controls. Erythrocyte glutathione peroxidase activity in selenium workers was significantly higher than in the control subjects. Urine selenium concentrations were not statistically different between the two groups. There was a significant positive correlation between plasma selenium concentrations and urine selenium concentrations in workers exposed to selenium. A weak significant positive correlation was found between plasma selenium concentrations and erythrocyte glutathione peroxidase activity in exposed workers. Our results suggest that the lower plasma selenium concentrations in selenium workers may be attributed to an increase of urinary selenium excretion.

Lead distribution in rats repeatedly treated with low doses of lead acetate.

Male Sprague-Dawley rats were treated with ip injections of lead acetate (10 and 20 mg/kg) at intervals of 1, 2, 4, 8, 12, 16, 20, and 24 weeks. Eight rats from each specified injection group were sacrificed 48 hr after the end of each treatment. Lead was determined in whole blood, plasma, plasma filtrate, saliva, urine, feces, brain, salivary glands, liver, kidney, testes, femur, and fur. In the liver, the concentrations of lead fluctuated; in the salivary glands and the testes, lead levels were low. In the bone, the kidney, and the brain, lead accumulated steadily and reached high levels in bone and renal tissues, but remained low in the brain. Correlation analysis showed a reciprocal relationship between blood-lead and kidney-lead in the rats treated with 10 mg lead acetate/kg (r = 0.898). In the rats treated with 20 mg lead acetate/kg, urine-lead was correlated to kidney-lead (r = 0.820). In both groups of treated rats, fur-lead was correlated to kidney-lead (r = 0.868 and r = 0.905, P less than 0.01) and brain-lead (r = 0.879 and r = 0.946, P less than 0.01).

Segmental and intracellular distribution of lead in rat kidney and salivary glands.

The segmental and intracellular distribution of lead (Pb) was studied in the kidney and salivary gland of Sprague-Dawley rats. Lead acetate was administered i.v. in a single dose (10 or 65 mg/kg body wt) or multiple biweekly doses (subchronic: 7 X 10 mg/kg over 3 months; chronic: 13 X 10 mg/kg over 6 months). Segments of cortical nephrons and salivary glands were separated following tissue slicing, incubation with collagenase and centrifugation on a Percoll density gradient medium. Subcellular fractions were obtained by differential centrifugation of renal and salivary tissue homogenates. Lead was predominantly localized in the renal proximal tubules, which contained at least twice as much of the metal as the distal tubules. Segment populations prepared from salivary tissues contained far less Pb than the renal fractions and showed no clear differences among themselves in their affinity for the metal. Intracellular Pb distribution was as follows: kidney nuclei (Nu) greater than mitochondria (Mt) greater than cytosol (Cy) greater than microsomes (Mc); salivary gland Cy greater than Mc greater than Mt greater than Nu. In most cases, 45Ca followed the same intracellular distribution as lead. Our data suggest that the proximal tubular segment may be the most likely renal target of chronic lead toxicity. The results point also to a much greater retention of Pb by the kidney than by salivary glands. The ability of the kidney to accumulate a great deal of lead to be released into tubular fluid over long periods, makes urinary lead a poor indicator of duration and frequency of exposure. On the other hand, the inability of salivary glands to retain this metal makes saliva lead concentration a potential indicator of current exposure.

Lead flux through the kidney and salivary glands of rats.

The blood disappearance curve of lead injected intravenously into rats and its appearance curve in the saliva reflect a three-compartment open model. Urinary elimination rate showed many fluctuations in the first 10 days but decreased progressively afterward. In clearance experiments, with low lead infusion (4 micrograms/min), renal reabsorption accounted for nearly all the filtered lead load, and salivary secretion was on the order of 1 ng/min. Experiments with renal and salivary tissue fragments indicated maximal accumulation in both tissues. Contrary to salivary tissue uptake, renal accumulation of lead decreased in the presence of KCN and 2,4-dinitrophenol, and in Na+-deficient media. Renal lead uptake contains, therefore, an important energy-dependent component. In vitro evidence that the lead transport mechanisms of the kidney and salivary glands are fundamentally different is consistent with the results of the pharmacokinetic study. The resemblance between the early profile of salivary lead secretion and its disappearance from the blood indicates that salivary glands represent diffusion barriers for the metal, in contrast to the kidney where lead uptake may be influenced by energy- and metabolism-dependent mechanisms.

Lead distribution in the saliva and blood fractions of rats after intraperitoneal injections.

Sprague-Dawley rats were treated with 1, 2 or 3 i.p. injections of lead acetate (100 mg/kg) and sacrificed 24 h, 3 days, 7 days, 14 days and 21 days after the last injection. Lead concentration was determined by flameless AAS technique in whole blood, plasma, plasma filtrate, saliva and submaxillary gland tissue. The concentration of lead in saliva was about 5% of whole blood lead concentration and around 61% of plasma filtrate lead level. Saliva lead concentration was significantly related both to whole blood lead concentration and plasma filtrate lead concentration (r = 0.78, P less than 0.001; r = 0.80, P = 0.001 respectively). Lead was present in the submaxillary gland tissue; the amount of lead increased with increasing amounts administered.

Lead levels in saliva and in blood.

The relation between salivary and whole-blood Pb levels was examined in 266 male adults, 196 of whom were Pb-exposed workers. The coefficient of correlation r between salivary and blood Pb levels was .72 (p less than 0.01); the correlation was improved when salivary Pb concentrations were plotted on a logarithmic scale. The results show that the salivary Pb concentration increased very rapidly, in a more or less exponential fashion, after blood Pb levels exceeded 500 micrograms/l. Techniques of saliva collection and Pb determination by flameless atomic absorption spectrophotometry are described. The validity of using salivary Pb as a screening test is evaluated.

Serum protein changes during exposure to ozone.

Serial measurements of serum proteins in rabbits exposed to 0.4 ppm and 1.0 ppm of ozone revealed progressive changes in the concentrations of the various fractions: albumine concentration declined while alpha- and gamma-globulin concentrations increased.