Microprobe studies of inorganic deposits in the aortic wall

The chemical composition and crystalline nature of inorganic deposits prese nt in the human aortic wall were investigated. A proton microprobe in combi nation with proton induced X-ray emission and proton induced gamma-ray emis sion were used to determine quantitatively the elemental composition of the inorganic deposits while their structure was studied with the use of an X- ray microprobe in combination with X-ray diffraction and Fourier transform infrared microscopy. It was found that deposits in the aortic wall are composed of Ca-P compound s. Fluorine is accumulated in the inorganic phase. However, the mechanism o f F deposition awaits further investigations. The only phase detected by th e X-ray diffraction was a defective hydroxyapatite. The relative intensitie s of reflexes indicate that the c axis of the crystallites is parallel to t he long axis of the vessel. IR microscopy revealed that the crystals were c ontaminated with carbonate groups. Moreover, the band characteristic for oc tacalcium phosphate was detected. (C) 2000 Elsevier Science B.V. All rights reserved.