Determination of metal uptake in single organisms, Corophium volutator, via complementary electrothermal vaporization/inductively coupled plasma mass spectrometry and laser ablation/inductively coupled plasma mass spectrometry.

RATIONALE: (Eco-)toxicological effects are mostly derived empirically and are not correlated with metal uptake. Furthermore, if the metal content is determined, mostly bulk analysis of the whole organism population is conducted; thus, biological variability is completely disregarded, and this may lead to misleading results. To overcome this issue, we compared two different solid sampling techniques for the analysis of single organisms. METHODS: In this study, complementary electrothermal vaporization/inductively coupled plasma mass spectrometry (ETV/ICP-MS) ⇔ laser ablation/inductively coupled plasma mass spectrometry (LA/ICP-MS)-based methods for the analysis of individual organisms were developed and the results obtained were compared with the concentrations obtained after digestion and measured using ICP-MS. For this purpose, a common (eco-)toxicological test organism, the mud shrimp Corophium volutator, was selected. As proof-of-concept application, these organisms were incubated with environmentally relevant metals from galvanic anodes, which are often used for protection against metal corrosion in, for example, offshore wind farms. RESULTS: The bulk analysis revealed that large quantities of the incubated elements were detectable. Using the ETV/ICP-MS method, we could identify a high biovariability within the population of organisms tested. Using the LA/ICP-MS method, it could be determined that the large quantities of the elements detected were due to adsorption of the metals and not due to uptake, which correlates well with the absence of (eco-)toxicological effects. CONCLUSIONS: The results obtained imply the efficiency of complementary methods to explain the absence or presence of (eco-)toxicological effects. In particular, methods that allow for single-organism analysis or provide even a spatial resolution support the interpretation of ecotoxicological findings.

Effects of Single Nucleotide Polymorphism Ala270Ser (rs316019) on the Function and Regulation of hOCT2.

The human organic cation transporter 2 (hOCT2) is highly expressed in proximal tubules of the kidneys, where it plays an important role in the secretion of organic cations. Since many drugs are organic cations, hOCT2 has relevant pharmacological implications. The hOCT2 gene is polymorphic, and the nonsynonymous single nucleotide polymorphism (SNP) causing the substitution of alanine at position 270 of the protein sequence with serine (Ala270Ser) is present with high frequency in the human population. Therefore, Ala270Ser has potentially important pharmacologic consequences. Here, we analyzed the transport properties and rapid regulation of hOCT2 wildtype and hOCT2 Ala270Ser expressed in human embryonic kidney cells using real-time uptake measurements. Moreover, we compared the expression of hOCT2 in the plasma membrane determined by biotinylation experiments and the cellular transport and toxicity of cisplatin measured by inductively coupled plasma mass spectrometry and a viability test, respectively. The transport characteristics and regulation of the wildtype and mutated hOCT2 were very similar. Interestingly, a higher affinity of hOCT2 Ala270Ser for creatinine was observed. Compared with hOCT2 wildtype, the plasma membrane expression, cisplatin transport, and cisplatin-associated toxicity of hOCT2 Ala270Ser were significantly lower. In conclusion, these findings suggest that Ala270Ser has subtle but important effects on hOCT2 function, which are probably difficult to detect in studies with patients.

Quantitative Bioimaging of Platinum via Online Isotope Dilution-Laser Ablation-Inductively Coupled Plasma Mass Spectrometry.

A new calibration strategy for elemental bioimaging based on online isotope dilution analysis (IDA) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) was developed and applied for the quantification of platinum in rat kidney tissues. A dry 194Pt spike aerosol was added in a post-cell setup, and the natural 194Pt/195Pt isotope ratio of the sample aerosol from laser ablation was changed accordingly. Spike mass flow determination was carried out based on reversed IDA using a reference standard. Quantitative data obtained by the new approach correlated well with those obtained by external calibration when analyzing parallel tissue slices of rat kidney from cisplatin perfusion studies. The novel quantification approach is traceable to SI units, as IDA is an definitive method. Signal drifts are compensated as the second isotope acts as an internal standard.

Quantitative Bioimaging to Investigate the Uptake of Mercury Species in Drosophila melanogaster.

The uptake of mercury species in the model organism Drosophila melanogaster was investigated by elemental bioimaging using laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). The mercury distribution in Drosophila melanogaster was analyzed for the three species mercury(II) chloride, methylmercury chloride, and thimerosal after intoxication. A respective analytical method was developed and applied to the analysis of the entire Drosophila melanogaster first, before a particular focus was directed to the cerebral areas of larvae and adult flies. For quantification of mercury, matrix-matched standards based on gelatin were prepared. Challenges of spatially dissolved mercury determination, namely, strong evaporation issues of the analytes and an inhomogeneous distribution of mercury in the standards due to interactions with cysteine containing proteins of the gelatin were successfully addressed by complexation with meso-2,3-dimercaptosuccinic acid (DMSA). No mercury was detected in the cerebral region for mercury(II) chloride, whereas both organic species showed the ability to cross the blood-brain barrier. Quantitatively, the mercury level in the brain exceeded the fed concentration indicating mercury enrichment, which was approximately 3 times higher for methylmercury chloride than for thimerosal.