Transport of lanthanides in milk into suckling rats.

The aim of this paper was to examine the transport of lanthanides in milk of contaminated rats into their sucklings and the retention of lanthanides in the sucklings. The research involved 55 female Wistar rats contaminated in the period of lactation and their offspring (400 infant rats). The study showed that in the period of lactation the transport in milk from the mother to the offspring of the lanthanide radionuclides under examination (144Ce, 147Nd, 152Sm, 155Eu and 160Tb) increased with their mass numbers: CE < Nd < Sm < Eu < Tb, and varied from 0.01% for 144Ce to 17.7% for 160Tb of the administered dose per litter. It was demonstrated that lanthanides were not absorbed from the digestive tract of sucklings because they were not detected beyond its area. Because of its highest concentration in milk 160Tb was chosen for further investigation of the kinetics of transport in individual segments of the digestive tract. The model for determining the function of lanthanide retention in separate parts of the digestive tract of sucklings and the half life of effective accumulation and elimination of 160Tb in the whole organism as well as in individual segments of the digestive tract are presented. Terbium-160 accumulation in sucklings increased whereas its elimination decreased with the age of the infant. No significant differences in 160Tb specific activity in stomach, and small and large intestines were observed in sucklings one to 21 days old. Biological half lives for retention of the contaminated milk were as follow: 0.25 +/- 0.021 per day for the stomach, 0.92 +/- 0.12 per day for the small intestine and 5.03 +/- 0.22 per day for the large intestine. The data obtained can be used in the evaluation of the doses absorbed from 160Tb and from other lanthanide radionuclides that are nonabsorbable from the digestive tract, as well as in estimation of the radiation risk to the offspring of mothers contaminated in the period of lactation.