Interactions between uranium and target cells: Example of UO4 particle transformation within alveolar macrophages. Interactions between uranium and target cells: examples of UO4 particle transformation within alveolar macrophages. 
The understanding of the mechanisms involved in the in vivo dissolution of inhaled particles is necessary to improve the model for determining the parameters. With that perspective, the intracellular transformation of UO4 particles has been investigated. Indeed, very few is known about this compound encountered in the nuclear fuel cycle. After instillation of UO4 particles in rats, alveolar macrophages and lung tissues have been observed. The particles break up very quickly in ultrafine particles and in some cases, this mechanism is accompanied by the formation of uranyl phosphate needles. This phenomenon takes place at very early stage, i.e., within the first 24 hours after the instillation. Particles phagocytised by macrophages in vitro have been observed after inclusion of the cells directly on the culture dish. These observations have confirmed the corrosive action exerted by the macrophages on the UO4 particles.