[In vitro uranyle affinity of per (3,6-anhydro-2-O-carboxyméthyle)-alpha-cyclodextrin and conditions required for in vivo application]

Per (3.6-anhydro-2-O-carboxymethyle)- alpha-cyclodextrin ([1]) is a polydentate analog of EDTA, a well-known cation chelating reagent. [1] exhibits strong affinities in vitro for lanthanids, cobalt and also for uranyl cations. Hence, a 1:1 stoechiometry and a high affinity for uranyle (6<logK<7) is found in vitro. Moreover, [1] is not hemolytic and exhibits not lettral properties in mice (LD(50)=42mM). In vivo injection at supralethal amounts of uranyl complex of [1] prevents immediate death in mice while unable to protect against later death. Pharmacocinetic studies show that a dissociation of the complex occurs lead to the release of free uranyle. Other complexation assays using [1] grafted tissues show that chelating properties for lead and uranyle differ from thoses observed in vitro.

[Methods to measure the cutaneous transfer of radionuclides across the intact or lesioned epidermis, application to radiotoxicology]

Although skin contamination by radionuclides is the most common cause of nuclear workers accidents, few studies dealing with the penetration of radioactive contamination through the skin are available. This work is a review of experimental methods that allow to assess transfer of radionuclides through the skin in occupational conditions, with or without skin trauma. The first section describes the different methods applied for skin transfer assessment of chemicals used in pharmacology. Major radionuclide contamination accidents can be associated with skin traumas. Thus, the second section describes the adaptation of these methods to radiotoxicology. Finally, the third section is an in vivo investigation of cobalt transfer (57CoCl2) through undamaged and damaged skin which simulates different industrial accident conditions (excoriation, acid or alcalin burn, scalding, branding).

[Efficiency of etidronic acid in the case of cutaneous radiocontamination by actinid elements: in vitro evaluation]

Ethane 1 hydroxy 1.1. biphosphonate (EHBP) is a medicine named Didronel, which inhibits bone resorption in the case of Paget's disease. This molecule could offer a new application in radiotoxicology. Our works describe its efficiency as decontaminating agent in uranium and plutonium cutaneous radiocontamination. Its effect on uranium and plutonium is demonstrated by two in vitro techniques using human cutaneous explants. Both techniques are usually used in dermopharmacology to estimate the action of topic drugs.

Contamination and decontamination of rat and human skin with plutonium and uranium, studied with a Franz's chamber

PURPOSE

Our work offers a new method of assessing human skin radiocontamination and of appraising its treatment. This in vitro technique stems from methods used in skin pharmacology.

MATERIALS AND METHODS

Franz's diffusion chambers, which help maintain the physiological condition of a skin biopsy, are used to study how 233U and 239Pu, added to a 0.1 N solution of nitric acid, could enter skin. The efficiencies of two different decontaminating agents (Na3Ca)DTPA (25%) and EHBP (0.5 M) are compared. These studies were made on human skin samples, recovered after plastic surgery. Parallel experiments were carried out on hairless rat skin biopsies and on the skin of live hairless rats.

RESULTS

Results in vivo and in vitro on the rat were not significantly different which validates the in vitro technique. In human beings, most of the radioactivity was found in the epidermis, with 2-4% found at the level of the dermis. By means of autoradiography we were able to identify that this radioactivity was concentrated in and around hair and sebaceous glands. Local treatments by EHBP seemed more efficient than those by DTPA in decorporating uranium and plutonium but the complexes radionuclide-EHBP seemed to diffuse through the skin more than the radionuclide-DTPA complexes if the skin was not rinsed after application of the chelating agent.

CONCLUSION

This new in vitro technique using human skin has been validated for radiotoxicology. It can be used to quantify the diffusion of radionuclides through the various skin layers and to assess the efficiency of decontaminating agents.

[Thorium a radioactive element in current use: physical-chemical properties and biological processing]

The radioactive properties and physicochemistry of thorium were studied and correlations drawn between thorium and element sof the titanium group, lanthanides and plutonium. It appears that the behavior of Th4+ and Pu4+ are similar, particularly their distribution pattern on bone surfaces. Chelating agents are reviewed and the structure of metal chelates indicated.