The X-ray absorption near edge structure (XANES) technique was applied in f
luorescence mode for the determination of the iron oxidation state in diffe
rent structures of the kidney. The experiment was performed on 20-mum thick
tissue sections at the National Synchrotron Light Source in Brookhaven Nat
ional Laboratory, USA with the use of a monochromatized beam around 7.2 keV
at the X26A beam line. The beam size was defined by four tantalum slits. T
he samples were taken from patients who were operated due to kidney cancer.
First, two-dimensional scans on the selected areas of the kidney tissue se
ctions were done in order to present distribution of iron concentration. Th
e scanned areas were visible on analyzed sections after the measurements al
lowing the precise matching of tissue structure with analytical data. Other
s successfully used similar matching procedures with the particle beams met
hods but synchrotron radiation is less damaging to biological materials. Th
en, the XANES spectra were taken on selected points that contained high con
centration levels of iron. The XANES measurements were done to determine th
e iron oxidation state. as this is regarded as one of the oxygen indicators
in tissue. and free radicals generation. In order to do so the spectra had
to be calibrated and normalized. Therefore, three standards were used. Fol
lowing previous work [Geochim. Cosmochim. Acta 58 (1994) 5209] a synthetic
fayalite [Fe2SiO4: standard for Fe(II)], pure magnetite [FeO . Fe2O3: stand
ard for a mixture of Fe(II) and Fe(III) with the ratio 1:2], and pure hemat
ite [Fe2O3: standard for Fe(III)] as standards for iron pre-edge peak posit
ion in the XANES spectra were used. It has been found that the iron concent
ration level is much higher in kidney glomeruli than in nephron regions and
due to XANES spectra analyses in the glomerular regions of the tissue sect
ions iron occurs in different oxidation states. (C) 2001 Elsevier Science B
.V. All rights reserved.