Quantitative bioimaging of copper in frozen liver specimens from cats using laser ablation-inductively coupled plasma-mass spectrometry

Abstract

Objectives: The aim of this study was to assess laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) as a tool for measuring concentrations and determining accumulation of copper in frozen liver specimens from cats. Methods: Six frozen liver specimens were evaluated by qualitative copper staining and quantitative flame atomic absorption spectroscopy. Tissue specimens were cryo-sectioned and quantitative bioimaging of copper was performed using LA-ICP-MS. Results were compared with those obtained using conventional methods. Results: Of the six specimens, only one showed positive staining for copper with rhodanine. Using flame atomic absorption spectroscopy (FAAS), one specimen showed a deficient copper level (<100 µg/g dry weight), two specimens had copper within the reference interval (RI; 150–180 µg/g) and three specimens had copper concentrations above the RI. Bioimaging from LA-ICP-MS showed inhomogeneous distribution of hepatic copper. The areas with dense copper accumulation were represented as hotspots in the liver specimens. Hepatic copper quantification by LA-ICP-MS correlated well with copper quantified by FAAS (r = 0.96, P = 0.002). Conclusions and relevance: Our findings suggest that quantitative bioimaging by LA-ICP-MS could be used to demonstrate the distribution and concentration of copper in frozen liver specimens from cats. The distribution of copper in these specimens was inhomogeneous with dense accumulation represented as hotspots on tissue sections. A positive correlation of hepatic copper concentrations determined by LA-ICP-MS and FAAS was found. Further studies to establish an RI for hepatic copper using this technique and to further determine its clinical utility are warranted.