아연결핍이 흰쥐에서 metallothionein의 발현과 카드뮴의 흡수 및 분포에 미치는 영향

Abstract

Zinc (Zn) is an essential element in biological process, however inadequate Zn status in general population have been recognized. To update the knowledge for Zn-cadmium (Cd) interaction, we studied the intestinal uptake and transport, and the expression of metal transporter proteins (divalent metal transporter 1, DMT1;metal transporter protein 1, MTP1; zinc transporter 1, ZnT1; metallothionein 1, MT1) in duodenum after Cd exposure using Zn deficient animal model. Rats were fed Zn deficient (ZnD, 0.5-1.0 mg Zn/kg) or Zn supplemented (ZnS, 50 mg Zn/kg) diet for 4 weeks, and followed single administration of 109CdCl2 orally. The body Zn status and tissue Cd concentration were determined at 24 hrs after Cd administration. Total body burden of Cd and Cd absorption index (AI, %) were estimated based on the tissue Cd analyzed. DMT1, MTP1, ZnT1 and MT1 mRNA were analyzed by using RT-PCR method. Feeding of Zn deficient diet for 4 weeks produced a reduced body weight gain and a depletion of body Zn. Tissue Cd concentration, body burden of Cd and Cd absorption index were higher in the ZnD diet fed rats than the ZnS diet fed rats. Especially, Cd concentration in the small intestine (duodenum, jejunum and ileum) and the colon of FeD diet fed rats were higher markedly than in the FeS diet group. The expression levels of DMT1, MTP1 and ZnT1 mRNA in FeD diet fed rats were similar to the FeS diet. The level of MT1 mRNA expression was significantly lower in the FeD than the FeS diet fed rats. Taken together, theses results indicate that Zn deficiency in diet induce an increased intestinal absorption and tissue retention of Cd, and down-regulate the MT1 expression in the intestine which might be play a part of role in Cd absorption and transport in mammalian. These findings suggest that deficiency of essential metal could be enhanced the toxicity of toxic, non-essstial metals through the metal-metal interaction.