Neptunium-237 Inhalation in Rats

Abstract

Groups of rats were exposed to aerosols of 237Np nitrate to determine clearance rates, retention and distribution at various intervals after inhalation. Initial lung burdens (ILB) after 237Np inhalation by three treatment groups were 0.12, 0.19 and 0.37 mu Ci/kg, respectively. Radiochemical analyses of animals killed at 4, 8, 14, 28 and 90 d, as well as data for others maintained until they became moribund, showed that their lung clearance followed a three-compartment model, clearance half-times for which were 1, 35, and 10,000 d, respectively. Only 3% of the ILB was retained after 90 d; 12% of that burden had translocated to the skeleton at 750 d; the half-time for skeletal retention was 2500 d. A single tumor was the only malignancy detected in the lungs of the 35 animals allowed to survive the early phase of the study.

ICRP Publication 141: Occupational Intakes of Radionuclides: Part 4

“…There was considerable rapid absorption (more than for the oxalate): at the first measurement (0.25 d), ∼70% ILD had deposited in the systemic tissues, mostly in the skeleton. Lung clearance was relatively slow thereafter, with retention decreasing to ∼13% ILD at 32 d and ∼1% ILD at 512 d. Analysis carried out here showed that the results could be fit with absorption parameter values as follows: f r was well defined at ∼0.7, s r was not well defined but >10 d −1 , and s s was not well defined but <0.002 d −1 . (625) Sullivan et al. (1986a) followed the tissue distribution of 237 Np up to 750 d after inhalation of 237 Np nitrate by rats at three exposure levels – high, medium, and low – with inhaled masses of ∼0.5, 0.25, and 0.17 mg 237 Np, respectively, per rat.…”

“…(625) Sullivan et al. (1986a) followed the tissue distribution of 237 Np up to 750 d after inhalation of 237 Np nitrate by rats at three exposure levels – high, medium, and low – with inhaled masses of ∼0.5, 0.25, and 0.17 mg 237 Np, respectively, per rat.…”

Revue des principales caractéristiques du237Np

“…Ainsi, la demi-vie de rétention pulmonaire du neptunium sous forme oxalate (4+) est supérieure à celle du nitrate (5+ et 6+) car celui-ci est plus facilement transportable vers le sang. Pour la forme nitrate et chez le rat, 23 % de la quantité déposée serait retenue dans le poumon après 4 jours, 13 % après 28 jours, et 2,5 9' 0 après 90 jours (Sullivan et al, 1986). De même, chez les animaux exposés à la forme aérosol, l'éli-mination pulmonaire était supérieure par rapport à l'intubation intratrachéale REVUE DES PRINCIPALES CARACTI?RISTIQUES DU 237Np de sels de neptunium ; toutefois, l'intubation utilise une concentration plus importante de radionucléide entraînant des dommages pulmonaires radioinduits, et affaiblissant les mécanismes de clairance (ICRP, 1986 ;Moskalev, 1979).…”

Le neptunium : pourquoi de nouvelles études ?

“…sée dans le poumon [1,45]. Là encore, la forme physico-chimique du composé inhalé influe directement sur son transfert vers le sang.…”