[Mechanisms of action for metallic elements and their species classified as R40 by EU]. / Meccanismi di azione cancerogena per elementi metallici e loro specie classificati R40--parte 3.

In this part of our survey we dealt with other metallic elements and species (antimony, lead and vanadium) classified by EU as R40 and not with the risk phrases R45 and R49. They are also differently considered by different Agency and Scientific Societies in respect to their carcinogenicity. Also for Pb, Sb, V and related species the carcinogenic effect is related with oxidation state, charge, the solubility, type of binding, stereochemistry. Some common mechanisms of carcinogenesis are the induction of oxidative stress, to inhibition of DNA repair, from activation of mitogenic signalling, to epigenetic modification of gene expression and each species lead to specific molecular interactions and were subject to different bioavailability. We focused in particular the mechanisms of action for lead, element moved in last IARC examination from group 2B to group 2A, with important potential consequences for EU classification In general for metallic elements even differently classified in respect to their carcinogenicity, knowledge of action mechanisms would give additional tools to reach more adequate risk assessment procedures and the preventive-health surveillance measures.

Vanadium speciation in serum by means of blue native gel electrophoresis.

Slab-gel electrophoresis has been applied to the speciation of vanadium in serum. The electrophoresis separation is an adaptation of the blue native polyacrylamide gel electrophoresis separation necessary to ensure the stability of the vanadium-protein complex; Coomassie blue was used to shift the charges of the proteins and to stabilize the vanadium complex. The detection of the vanadium species was made possible by the use of the (48)V radiotracer and the phosphor-screen technology. The method was first developed using transferrin, incubated with (48)V, as a model. After it was proved that the vanadium-transferrin complex was stable during separation, the method was validated by separating serum incubated with (48)V. The efficiency of the separation was assessed according to two parameters: resolution and conservation of the species. First, the resolution of the separation was as expected from a native separation. Second, the release of free vanadium from the transferrin complex, which was the main vanadium species expected, was negligible, which proves that the species remain intact during separation. In accordance with the literature, it was found that vanadium binds to transferrin in incubated serum at these low concentrations.

Speciation of vanadium(IV) and vanadium(V) using ion-exchange chromatography and ICP-AES.

A speciation method for vanadium(IV) and vanadium(V) is presented that uses a combination of HPLC and ICP-AES. In this method, 1 mM HNO3 solution and 100 mM HNO3 solution were applied in sequence as eluent. A vanadium(IV) and vanadium(V) mixture was injected into a HPLC anion-exchange column; and vanadium(IV) cation was then eluted by 1 mM HNO3, while vanadium(V) oxoacid anion was trapped on the column. After this separation, vanadium(V) was eluted as a cation from the column by 100 mM HNO3. Vanadium was detected by ICP-AES. In this separation, about 15% of vanadium(V) interfered with vanadium(IV), and trace vanadium(IV) interfered with vanadium(V). This interference could be estimated by simple calculation based on standard observations, and the speciation of vanadium(IV) and vanadium(V) was performed. The lower determination limit was 1 microgram/mL, which is insufficient to speciate vanadium sampled by conventional sampling methods in a working environment. However, impurity of the other valent vanadium species in a vanadium(V) reagent can be determined by the present method, which should be valuable in precisely assessing the toxicities of vanadium species.