Speciation of arsenic and selenium in rabbit using x-ray absorption spectroscopy
Abstract
Chronic arsenic poisoning due to arsenic contamination of groundwater is a serious
public health problem in Bangladesh and neighboring countries. Severe health effects
associated with chronic exposure to arsenic include melanosis and several kinds of cancer.
It is now generally agreed that the arsenic contamination of groundwater in Bangladesh is
of geological origin. Arsenic naturally present in aquifers may be mobilized into drinking
water by microbial action.
The formation of a novel arsenic-selenium compound: seleno-bis (S-glutathionyl)
arsinium ion, [(GS)2AsSe]-, and its subsequent excretion in rabbit bile has been
demonstrated previously. This molecular basis for the in vivo antagonism between
arsenic and selenium was discovered using X-ray absorption spectroscopy. There is
growing evidence that, in Bangladeshi people who are suffering long term chronic lowlevel
arsenic poisoning, this antagonism is causing a selenium deficiency. Administering
selenium supplements might provide a simple but highly effective treatment of the
Bangladeshi arsenic poisoning.
In order to examine the disposition of [(GS)2AsSe]-, a set of rabbits were
intravenously injected with selenite, arsenite or both. Whole blood, red blood cell and
plasma samples were collected at different time intervals within 2hrs after injection and
cecotrope samples 24hr after injection. Samples were examined using X-ray absorption
spectroscopy and both arsenic and selenium K-near edge spectra were recorded.
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Speciation of arsenic and selenium will be discussed in this thesis. Results indicate that
[(GS)2AsSe]- is formed in blood very rapidly after injection of both arsenite and selenite,
and then is removed from blood stream within 2hrs post injection. Results also show that
[(GS)2AsSe]- is assembled in red blood cells, with no [(GS)2AsSe]- detected in plasma
samples. [(GS)2AsSe]- is also found in cecotrope samples after injection of both arsenite
and selenite.
The results of this study in rabbits will contribute to the understanding of chronic
arsenic poisoning in humans.