Gastrointestinal absorption and retention of polonium in adult and newborn rats and Guinea pigs

The gastrointestinal absorption of ²¹⁰Po was determined by comparing tissue retention after oral and systemic administration. The results indicate an increase in absorption in adult rats for ²¹⁰Po administered in liver compared with ²¹⁰Po nitrate with estimated absorption of 5 and 13%, respectively. For ²¹⁰Po citrate, values of about 7% were obtained 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 ²¹⁰Po in neonates was high in rats but not guinea pigs. In adult animals, but not neonates, the liver accounted for a greater proportion of ²¹⁰Po reaching the bloodstream after ingestion than after systemic injection. The significance of these results is discussed in relation to current assumptions made in the calculation of doses from ²¹⁰Po.