Some recent data on chemical protection against ionizing radiation.

Once introduced in the organism, the radioprotectors are fastly degraded and that increases their toxicity, shortens their duration of action and renders them inactive after oral delivery. So, it was tried to protect them by their incorporation in vectors. When a cysteamine-liposomal suspension was orally delivered, it showed a radioprotective activity for about 4 hours. By using 35S cysteamine, it was noted that its plasmatic concentration was increased. Freeze-drying of these preparations was a good mean of conservation if the samples were stored at 4 degrees C. A good and sustained activity was also obtained after oral delivery of WR-2721 entrapped in microspheres. Otherwise, it was shown that after interacting with the polar heads of phospholipids, under determined conditions of pH and in fluid phase, aminothiols can penetrate inside the membrane and be entrapped in the internal medium of liposomes and as they penetrate, they can lessen the diffusion of oxygen in the lipidic bilayers.