Endocrine Abstracts

Uranium is the heaviest naturally occurring element found in the Earth’s crust. It is an alpha-emitter radioactive element that present both radiotoxicant and chemotoxicant properties. Uranium is present in environment as a result of natural deposits and releases by human applications (mill tailings, nuclear industry and military army). Populations could thus be exposed to uranium either through their drinking water or the food chain.

Natural uranium can be radiologically enriched, the by-product of this enrichment is then called depleted uranium. Enriched uranium is three time more radioactive than depleted uranium.

Few studies have been conducted regarding the effects of uranium contamination on reproduction or steroidogenesis. Hormonal levels were modified among uranium miners, whereas no effects were observed in Gulf war veterans with retained fragments of depleted uranium shrapnel.

To distinguish chemical versus radiological effects of uranium on the metabolism of the steroids in the testis, rats were contaminated via their drinking water with depleted or enriched uranium. Animals were exposed to radionuclides for 9 months at a dose of 40 mg/l (560 Bq/l for depleted uranium, 1680 Bq/l for enriched uranium). This dose represent double highest concentration find in some wells of Finland.

While depleted uranium did not seem to significantly affect the production of testicular steroid hormones in rats, enriched uranium significantly increased the level of circulating testosterone. Enriched uranium contamination pointed out significant increases in the mRNA levels of synthesis enzymes, while depleted uranium contamination induces no change in these genes expression. Moreover, expression levels of nuclear receptors, as well as the transcription factors were modified following enriched uranium contamination.

In conclusion, our results show for the first time a differential effect among depleted or enriched uranium contamination on the testicular steroidogenesis. This study didn’t show pathological consequences, but raises questions about the of uranium chronic contamination on human being.