Micro-PIXE imaging of the rib bones of rats

The ribs are bones that constitute the ribcage and consist of three regions: cartilage, costochondral junction with growth plate structures, and hard bone. In this study, frozen sections of rat ribs were prepared, and the distributions of calcium (Ca), phosphorus (P), potassium (K), and sulfur (S) were examined using particle-induced X-ray emission with microprobe (micro-PIXE) analysis. Areas with high Ca and P accumulation were observed in the interior of the rib cartilage. Histograms comparing the Ca accumulation in the three rib regions showed that the mode of accumulation of Ca in the cartilage are similar to that of the costochondral junction but distinct from that of the hard bone. The cartilage section did not possess an alkaline phosphatase-concentrated area that reflects the hard bone mineralization and is enriched in the costochondral junction. These data indicate differences in the mineralization process between cartilage and hard bones.