Use of proliferation tests to evaluate the effects of complexing agents on beryllium toxicity.

Occupational exposure to beryllium may cause chronic beryllium disease (CBD), a granulomatous interstitial pneumonitis caused by a cell-mediated immune response with delayed hypersensitivity initiated by an electrostatic interaction with the MHC class II human leukocyte antigen (HLA). Increased research efforts focus on the development of a CBD treatment by chelation therapy. This work presents an in vitro evaluation of the beneficial effects of beryllium chelation with different organic substrates. We have used a standard beryllium lymphocyte proliferation test (BeLPT) adapted for mouse splenocytes. Three complexing agents, 4,5-dihydroxy-1,3-benzenedisulfonic acid (tiron), nitrilotripropionic acid (NTP) and nitrilotriacetic acid (NTA), were tested using different protocols of the splenocyte proliferation test (SPT). We studied their corrective effect (beryllium pre-exposed splenocytes), their protective effect (ligand pre-exposed splenocytes) and their combined effects at fixed Be:L ratio of 1:2, at fixed Be concentration and at fixed L concentration. We also studied the effect of tiron in preventing splenocyte sensitization to beryllium. All three complexing agents showed a corrective effect and proved efficient in the combined effects, except NTA in the fixed Be:L ratio. Only NTP and tiron showed a significant protection at lower beryllium concentrations, while NTA was not significant. Splenocytes pre-exposed to chelated beryllium did not show sensitization while splenocytes pre-exposed to beryllium were sensitized. We observed a strong correlation between the efficiency of the complexing agent and its affinity towards beryllium. Both tiron and NTP showed a similar affinity towards the beryllium ion that is 10(7) higher than that of NTA.

Graphite furnace atomic absorption spectrometry as a routine method for the quantification of beryllium in blood and serum.

BACKGROUND: A routine method for the quantification of beryllium in biological fluids is essential for the development of a chelation therapy for Chronic Beryllium Disease (CBD). We describe a procedure for the direct determination of beryllium in undigested micro quantities of human blood and serum using graphite furnace atomic absorption spectrometry. Blood and serum samples are prepared respectively by a simple 8-fold and 5-fold dilution with a Nash Reagent. Three experimental setups are compared: using no modifier, using magnesium nitrate and using palladium/citric acid as chemical modifiers. RESULTS: In serum, both modifiers did not improve the method sensitivity, the optimal pyrolysis and atomization temperatures are 1000 degrees C and 2900 degrees C, respectively. In blood, 6 microg of magnesium nitrate was found to improve the method sensitivity. The optimal pyrolysis and atomization temperatures were 800 degrees C and 2800 degrees C respectively. CONCLUSION: In serum, the method detection limit was 2 ng l(-1), the characteristic mass was 0.22 (+/- 0.07) pg and the accuracy ranged from 95 to 100%. In blood, the detection limit was 7 ng l(-1), the characteristic mass was 0.20 (+/- 0.02) pg and the accuracy ranged from 99 to 101%.

Study on the effects of nitrilotriproprionic acid and 4,5-dihydroxy-1,3-benzene disulphonate on the fractionation of beryllium in human serum using graphite furnace atomic absorption spectrometry.

BACKGROUND: Occupational exposure to beryllium may cause Chronic Beryllium Disease (CBD), a lung disorder initiated by an electrostatic interaction with the MHC class II human leukocyte antigen (HLA). Molecular studies have found a significant correlation between the electrostatic potential at the HLA-DP surface and disease susceptibility. CBD can therefore be treated by chelation therapy. In this work, we studied the effect of two complexing agents, nitrilotriproprionic acid (NTP) and 4,5-dihydroxy-1,3-benzene disulphonate (Tiron), on the fractionation of beryllium in human serum analysed by graphite furnace atomic absorption spectrometry (GFAAS). RESULTS: We found the average serum beryllium concentration of fourteen non-exposed individuals to be 0.53 (+/- 0.14) microg l(-1), with 21 (+/- 3)% of the beryllium mass bound to the low molecular weight fraction (LMW), and 79 (+/- 3)% bound to the high molecular weight fraction (HMW). The addition of Tiron increased the beryllium mass in the HMW fraction, while NTP was not seen to have any influence on the fractionation of beryllium between the two fractions. NTP was, however, shown to complex 94.5% of the Be mass in the LMW fraction. The beryllium GFAAS detection limit, calculated as three times the standard deviation of 10 replicates of the lowest standard (0.05 microg L(-1)), was 6.0 (+/- 0.2) ng L(-1). CONCLUSION: The concentration of beryllium or its fractionation in human serum was not affected by sex or smoking habit. On average, three quarters of the beryllium in serum were found in the HMW fraction. Of the two ligands tested, only Tiron was effective in mobilising beryllium under physiological conditions, thus increasing the Be content in the HMW fraction.