Miller W J, Blackmon D M, Gentry R P, Pate F M
Department of Animal and Dairy Science, University of Georgia, Athens 30602.
J Dairy Sci. 1991 Oct;74(10):3535-43. doi: 10.3168/jds.S0022-0302(91)78545-7.
Zinc metabolism was studied in Zn-deficient and control Holstein calves over a 2-mo period following a single oral or i.v. 65Zn dose. In both orally and i.v. dosed animals, all gastrointestinal tissue sections from Zn-deficient animals contained more 65Zn than comparable tissues of controls. Contents of proximal small intestinal sections of Zn-deficient calves contained more 65Zn 8 to 10 wk after dosing than did those from controls; however, the reverse occurred in the distal small intestine, cecum, and large intestine. With both dosing methods, Zn-deficient calves retained more 65Zn throughout the study. Daily 65Zn excretion rate as a percentage of that retained declined for 6 wk after dosing, indicating a constantly increasing biological half-life. For deficient calves, the biological half-life was about 500 d in the later weeks of the experiments. In orally dosed, Zn-deficient animals, specific activity of fecal 65Zn exceeded that of serum Zn throughout the study. This shows a shortcoming in the basic assumption of measuring endogenous Zn loss from fecal and serum specific activities and total fecal stable Zn. Thus, endogenously excreted Zn is not representative of that remaining.
在给荷斯坦犊牛单次口服或静脉注射65Zn剂量后的2个月期间，对缺锌和对照犊牛的锌代谢进行了研究。在口服和静脉注射给药的动物中，缺锌动物的所有胃肠道组织切片所含的65Zn均比对照动物的相应组织多。给药后8至10周，缺锌犊牛近端小肠切片的65Zn含量高于对照犊牛；然而，在远端小肠、盲肠和大肠中则出现相反情况。两种给药方法下，缺锌犊牛在整个研究过程中保留的65Zn更多。给药后6周内，每日65Zn排泄率占保留率的百分比下降，表明生物半衰期不断延长。在实验后期几周，缺锌犊牛的生物半衰期约为500天。在口服给药的缺锌动物中，整个研究过程中粪便65Zn的比活性超过血清锌。这表明在通过粪便和血清比活性以及粪便总稳定锌来测量内源性锌损失的基本假设中存在缺陷。因此，内源性排泄的锌并不代表剩余的锌。
