Excretion and tissue distribution of selenium following treatment of male F344 rats with benzylselenocyanate or sodium selenite.

Benzylselenocyanate (BSC), a synthetic organoselenium compound less toxic than sodium selenite (Na2SeO3), has been demonstrated to inhibit the development of neoplasia in several experimental animal models. We examined the excretion and tissue distribution of total Se after acute administration of BSC compared to Na2SeO3. Male F344 rats were treated po with approximately one-tenth of the LD50 values, our estimate of highest non-toxic dose. The doses administered were 9.85 mg/kg in the case of BSC and 4.35 mg/kg in the case of Na2SeO3. The rats were sacrificed at 1, 6, 24, 72, or 120 hr to obtain biological samples. The levels of total Se were determined by graphite furnace atomic absorption spectrophotometry following microwave digestion. In serum, the highest Se level was observed at 6 hr after administration of either BSC or Na2SeO3: 1.34 +/- 0.07 (mean +/- SE), or 2.09 +/- 0.11 micrograms/ml of serum, respectively. In urine and feces, the cumulative percentages of doses excreted within 3 days of BSC or Na2SeO3 treatment were, respectively, as follows: 11.36 +/- 0.82% and 18.33 +/- 0.77% in urine; and 6.67 +/- 0.66% and 31.14 +/- 4.66% in feces. Among the tissues of BSC-treated rats, the kidneys were found to have the highest Se levels throughout the experimental period (as much as 29 micrograms/g of tissue at 72 hr), followed by liver, small intestine, large intestine, lung, pancreas, heart, and spleen. The results indicate that Se from BSC-treated animals is excreted very slowly and is retained in the organs for a much longer period compared to rats treated with Na2SeO3. Whether the slow excretion and prolonged retention of BSC and/or its metabolites play a role in its chemopreventive action is currently under investigation.