Tamano H, Igasaki E, Enomoto S, Oku N, Itoh N, Kimura T, Tanaka K, Takeda A
Riken (Institute of Physical and Chemical Research), Wako, Saitama, 351-0198, Japan.
Biochem Biophys Res Commun. 2000 Apr 21;270(3):1140-3. doi: 10.1006/bbrc.2000.2557.
Based on previous findings that liver zinc and metallothionein (MT) levels increase after tumor transplantation, zinc metabolism in tumor-bearing mice was studied to clarify the role of zinc-MT in host defense systems. Zinc in the hepatic cytosolic MT fraction did not increase in tumor-bearing mice fed a zinc-deficient diet, suggesting that dietary zinc is necessary for apo-MT induction in the liver after tumor transplantation and is then incorporated into the apo-MT. When (65)ZnCl(2) was intravenously injected, liver (65)Zn levels in the tumor-bearing mice were higher than those in control mice for 72 h after the injection. Pancreatic and blood (65)Zn levels in tumor-bearing mice were lower than those in controls for 24 h (pancreas) and 6 h (blood) after the injection. These findings indicate that the hepatic zinc response via MT induction influences zinc metabolism in the body after tumor transplantation. Moreover, (65)Zn uptake in the liver of MT-deficient tumor-bearing mice was lower than that in control tumor-bearing mice 1 h after injection. (65)Zn uptake in the tumor and blood (65)Zn levels in the MT-deficient tumor-bearing mice were higher than those in the control tumor-bearing mice. Tumor weight increased more in MT-deficient mice than in control mice. The formation of zinc-MT in the liver of tumor-bearing mice might decrease blood zinc availability for tumors and other tissues, such as the pancreas.
基于先前的研究结果，即肿瘤移植后肝脏锌和金属硫蛋白（MT）水平会升高，本研究对荷瘤小鼠的锌代谢进行了研究，以阐明锌-MT在宿主防御系统中的作用。在喂食缺锌饮食的荷瘤小鼠中，肝细胞质MT组分中的锌没有增加，这表明饮食中的锌对于肿瘤移植后肝脏中脱辅基MT的诱导是必需的，然后被整合到脱辅基MT中。静脉注射（65）ZnCl2后，荷瘤小鼠肝脏中的（65）Zn水平在注射后72小时内高于对照小鼠。注射后24小时（胰腺）和6小时（血液），荷瘤小鼠胰腺和血液中的（65）Zn水平低于对照小鼠。这些发现表明，通过MT诱导的肝脏锌反应会影响肿瘤移植后体内的锌代谢。此外，注射后1小时，MT缺陷型荷瘤小鼠肝脏中的（65）Zn摄取低于对照荷瘤小鼠。MT缺陷型荷瘤小鼠肿瘤中的（65）Zn摄取和血液中的（65）Zn水平高于对照荷瘤小鼠。MT缺陷型小鼠的肿瘤重量比对照小鼠增加得更多。荷瘤小鼠肝脏中锌-MT的形成可能会降低肿瘤和其他组织（如胰腺）的血液锌可用性。
