GASTROINTESTINAL ABSORPTION AND RETENTION OF POLONIUM IN ADULT AND NEWBORN RATS AND GUINEA-PIGS

The gastrointestinal absorption of Po-210 was determined by comparing tissue retention after oral and systemic administration. The results i ndicate an increase in absorption in adult rats for Po-210 administere d in liver compared with Po-210 nitrate with estimated absorption of 5 and 13%, respectively. For Po-210 citrate, values of about 7% were ob tained in 1-day-old neonate and adult rats while absorption in guinea pigs was estimated to be about 23% in 1-day-old neonates, 17% in 5-day -old neonates, and 9% in adults. Gut retention of ingested Po-210 in n eonates was high in rats but not guinea pigs. In adult animals, but no t neonates, the liver accounted for a greater proportion of Po-210 rea ching the bloodstream after ingestion than after systemic injection. T he significance of these results is discussed in relation to current a ssumptions made in the calculation of doses from Po-210.