43 MTs serve as cellular regulators by coordination of essential metals (Zn, Cu) and reducing the toxicity of heavy metals (Cd, Pb) [3]. MTs can be detected electrochemically in Brdicka solution. Here, three characteristic signals are measured for construction of elect- rochemical fngerprint of MT: RS 2 Co (about -1.3 V), Cat1 (-1.4 V) and Cat2 (-1.5 V). Te obtained voltammograms are then analyzed by mathe- matical model [4,5]. Cadmium (Cd), a non-essential heavy metal and a selective toxicant, is accumulated mainly in the kidneys where it causes cellular injury [6]. Cd ions stimulate expression of MTs and toxicity occurs when the concentration of Cd ions exceeds the bufering capacity of intrace- llular MTs [7]. Cd naturally occurs in the en- vironment as a pollutant from agriculture and industry [8-10]. Cadmium is a known teratogen MALDI-TOF MSI and electrochemical detection of metallothionein in chicken liver afer cadmium exposure Roman Guran 1,2 *, Iva Blazkova 1,2 , Renata Kensova 1,2 , Lukas Richtera 1,2 , Lucie Blazkova 1,2 , Ondrej Zitka 1,2 , Rene Kizek 1,2 and Vojtech Adam 1,2 1 Department of Chemistry and Biochemistry, Mendel University in Brno, Zemedelska 1, 613 00 Brno, Czech Republic; E-Mails: iva.blazkova@seznam.cz (I.B.), R.Kensova@seznam.cz (R.K.), oliver@centrum. cz (L.R.), BlazkovaLu@seznam.cz (L.B.), zitkao@seznam.cz (O.Z.), kizek@sci.muni.cz (R.K.), vojtech. adam@mendelu.cz (V.A.) 2 Central European Institute of Technology, Brno University of Technology, Technicka 10, 616 00 Brno, Czech Republic * Author to whom correspondence should be addressed; E-Mail: r.guran@email.cz; Tel.: +420 545 133 350; Fax: +420 545 212 044. Received:10.9.2015 / Accepted:20.9.2015 / Published:1.10.2015 Keywords: metallothionein; Cd toxicity; chicken liver; MALDI MSI 1. Introduction Metallothioneins (MTs) are intracellular, low- -molecular weight, proteins where cysteines form at least one third of all protein amino acids and thiol groups serve as pockets for co- ordination with divalent metal ions, especially Zn and Cu [1]. Metallothioneins are connected with cancer development, protection of orga- nism against environmental pollution efects and also with chemoresistance of cells. Teir main functions include detoxifcation of heavy metals, maintenance of ion homeostasis and protection against oxidative stress. MTs exist in all kind of mammalian cells. Four isoforms of human MT (MT-1, MT-2, MT-3, MT 4) were found so far [2] and according to UniProt da- tabase two chicken MTs (MT1 and MT3) have been reported. Te expression of MTs in the li- ver can be induced by several metals and drugs. Metallomics is an area that studies the interactions of metal ions with proteins and other biomolecules and their function in living organisms. Metallothioneins (MTs) belong to a large family of metalloproteins in this feld. As it is known, the presence of Cd 2+ ions causes higher expression of MTs. Terefore we focused on determination of MT and Cd content in liver from chicken embryos (model organism) by electrochemistry and atomic absorption spectroscopy (AAS) afer the exposure of chicken embryos to diferent concentrations of Cd(NO 3 ) 2 . We also determined the spatial distribution of MT in chicken liver tissue slices by matrix assisted laser desorption/ionization time-of-fight mass spectrometry imaging (MALDI-TOF MSI) and evaluated the toxicity of Cd(NO 3 ) 2 to chicken embryos. Finally, we attempted to fnd the correlation between 2D MSI maps of MT and concentration of MT in chicken liver. ARTICLE