Metabolism of zinc-65

Abstract

The absorption, deposition, and excretion of zinc65 was studied in mice, rats, and dogs. When zinc65 was fed to the animals it was poorly absorbed, but its long biologic half-life made even the small portion absorbed physiologically significant. Absorption was obviated by feeding large quantities of nonradioactive carrier zinc. Injected zinc65 chloride first was deposited, preferably in the pancreas, liver, and spleen, with only minor deposition in muscle and in the brain. Subsequently, a large proportion was transferred to bone. The chief means of excretion was in feces, presumably via pancreatic secretion. Injected nonradioactive zinc or treatment with 2,3-dimercaptopropanol (BAL), Versene, or cadmium ion failed to alter body burden significantly. Cadmium, however, decreased soft tissue zinc65 deposition and increased accretion by the skeleton. Blood activity fell rapidly and less than .01% of the dose injected remained in the blood after 1 day. Renal excretion of zinc65 rose as plasma concentration fell and clearance ratios in excess of 1.0 were noted, indicating probable renal secretion.

A LITERATURE REVIEW OF $sup 65$Zn IN BIRDS WITH SPECIAL REFERENCE TO THE MALLARD.

“…McDonald et al (1966) presented the zinc concentration in the animal body along with other essential elements (Table 9). Sheline et al (1943) and Rubini et al (1961) found 65 Zn injected in the mouse and dog was accumulated first in the liver, pancreas and spleen, with later transfer to bone, skin, and skeletal muscles. As liver, pancreas, spleen and kidney tissue declined in 65 Zn activity, other tissues slowly began to accumulate radioactive zinc.…”

“…Absorption of 65 Zn from the gastro-intestinal (G.I.) tract generally is low, but due to its long biological half life small assimilated quantities are of physiological significance (Rubini et al, 1961). In attempting to learn more of the role of zinc in the metabolism of vertebrates, much laboratory work has been carried out on chicks (Roberson and Schaible, 1958;Rahman et al, 1959;Kienholz et al, 1964;Turk, 1963Turk, , 1964and Ziegler et al, 1964), rats (Stirn, 1935;Feaster et al, 1955;Ballou, 1958Ballou, , 1960Taylor, 1961;, and mice (Sheline et al, 1943;Cotzias et al, 1962;and Richmond etal., 1962).…”

“…Miller and Cragle, 1965Miller and Cragle, 1965Miller and Cragle, 1965Curnow et al, 1967Hoekstra, 1964Graham and Telle, 1967Graham and Telle, 1967Feaster et al, 1955Ballou, 1960Ballou, 1960Ballou, 1960Ballou, 1960 Zinc stored in bone may be removed for utilization in zinc deficient body systems thus lowering the bone concentration of zinc in favor of zinc maintenance in soft tissues. Studies of 65 Zn metabolism in mice, rats, and dogs (Rubini et al, 1961) indicated that absorption of the radionuclide was hindered by feeding amounts of carrier zinc in excess of nutritional re- quirements. In the same light, Ballou (1958, 3) found, from his work on zinc metabolism in rats, ".…”

Pharmacokinetics of Intravascularly Administered 65Zinc in Channel Catfish (Ictalurus punctatus)

“…Previous studies have reported either relatively short (a few weeks) or long (several months) half-lives of zinc in both mammals and "sh, depending on the test species and experimental design (Rubini et al, 1961;Shulman et al, 1961;Andermann and Dietz, 1982;Alsop et al, 1999). For example, whole-body measurements of the half-life of Zn in small "sh range from 13 days in silversides Menidia menidia (Shulman et al, 1961) to greater than 6 months in mosquito"sh Gambusia holbrooki ( formerly, G. a.nis) (Willis and Jones, 1977;Newman and Mitz, 1988).…”

“…In mammalian species, zinc initially accumulates in the liver, kidney, pancreas, and spleen within the "rst 2 to 24 h of exposure and then is redistributed to bone (Gregus and Klaasen, 1986;Hammond and Beliles, 1980;Rubini et al, 1961;Guillard et al, 1984). Intravascularly (iv) administered zinc in rats was primarily excreted in the feces (31% of dose) during the "rst 4 days of elimination, and renal and biliary excretion were minor ( 42% of dose) (Gregus and Klaassen, 1986).…”