Iron localization in the guinea pig choroid plexus: A light and transmission electron microscopy study

The role of the choroid plexus (CP) in iron (Fe) homeostasis has been suggested as the main mechanism of Fe uptake and storage in the mammalian central nervous system. Thus, the CP of the lateral and fourth ventricles was studied in guinea pigs with light and electron microscopy using methods including Perls' Prussian blue and Gomori acid phosphatase staining, immunoreactivity for ferritin and transferrin, as well as energy dispersive spectrometry microanalysis. The present study reveals the presence of endogenous Fe in CP epithelial cells. Under light microscopy, Prussian blue staining revealed dark blue precipitates (i.e., Fe3+) with a preferentially perinuclear localization. The Fe was also positive for such granules with similar cellular localization. Ultrastructural analysis demonstrated the presence of dense bodies and siderosomes with molecular ferritin. The spectra obtained by the microanalysis demonstrated emissions for Fe, both in dense bodies and siderosomes. This study suggests that guinea pig CP epithelial cells accumulate Fe in the form of ferritin, possibly in cytoplasmic organelles such as lysosomes.