Absorption, Excretion, and Tissue Deposition of Titanium in Sheep

Abstract

Titanium metabolism was measured in three 18 kg lambs each fed 450 g chopped hay daily. Two of the lambs were dosed orally and one intravenously with 3 muCi titanium-44 each. Clearance of the intravenous dose was extremely slow; after oral administration, however, no titanium-44 was detected in blood plasma for 48 h. Over 96% of the oral dose was recovered in feces and digestive tract contents. Titanium-44 absorption, estimated from total carcass recovery and by comparison of concentrations in internal organs of orally and intravenously dosed lambs, was less than .5%. Fecal titanium could be a satisfactory index of soil ingestion by grazing ruminants.

ICRP Publication 151: Occupational Intakes of Radionuclides: Part 5

“…(173) Miller et al (1976) determined the distribution of 44 Ti in lambs after oral or intravenous administration of 44 TiCl 4 . At 2 d after oral administration, the mean activity concentration in systemic tissues, normalised to 1.0 for the liver, decreased in the order: liver (1.0) > kidneys (0.74) > pancreas (0.49) > spleen (0.28) > lung, heart, and adrenals (<0.15).…”

“…Miller et al, 1976;Zhu et al, 2010;Golasik et al, 2016a,b), as such studies may be most appropriate for assessing the fate of radiotitanium in the body. The initial distribution of titanium is based mainly on the results of Miller et al (1976), which suggest that the initial distribution of systemic titanium is similar but not identical to that of zirconium as depicted in the biokinetic model for systemic zirconium in Publication 134 (ICRP, 2016). The long-term kinetics of titanium are based on relative concentrations of titanium in tissues as determined in the autopsy study of Zhu et al (2010).…”

Metabolic data for titanium

“…If the value of 10 pg is taken as representative this would indicate that the fractional absorption of dietary titanium is probably about 0.01. A fractional absorption of 0.01 was obtained in experiments in which sheep ingested titanium chloride (Miller, Madsen and Hansard, 1976). In this reportf, is taken to be 0.01 for all compounds of titanium.…”

“…In lambs, injected intravenously with TiCl, and killed 48 h later, about 0.25 of the titanium was found in the skeleton, 0.18 in blood, 0.13 in skeletal muscle and 0.11 in internal organs (Miller, Madsen and Hansard, 1976). In mice, chronically exposed to titanium in drinking water, none of the tissues examined seemed to preferentially concentrate the element to any appreciable extent (Schroeder, Balassa and Tipton, 1963).…”

“…In lambs, only about 0.04 of intravenously injected titanium is excreted in the first 2 days after injection (Miller, Madsen and Hansard, 1976). Data on the body content and daily intake of titanium of Reference Man (ICRP, 1975) suggest, when taken in conjunction with anfi of 0.01, that the biological half-life of titanium in the body is about 600 days.…”