Dietary zinc deficiency and repletion modulate metallothionein immunolocalization and concentration in small intestine and liver of rats

Metallothionein (Mt) functions in zinc (Zn) homeostasis and dietary Zn affe cts tissue MT concentration. The objective of this study was to investigate the effects of dietary Zn deficiency and 24-h Zn repletion on MT immuno lo calization and concentration in the small intestine and liver of growing ra ts. Three-week-old rats fed Zn-deficient diet (< 1 mg Zn/kg) for 16 d had n o MT staining in either small intestine or liver. After 24-h Zn repletion w ith control diet (30 mg Zn/kg), strong MT staining was observed in intestin al Paneth cells and surface epithelial cells in the proliferative regions o f villi. Pair-fed control rats had strong MT staining in liver that was loc alized around central veins. After 24-h energy repletion, the hepatic MT st aining diminished. Furthermore, Zn-deficient rats had significantly reduced intestinal (57%) and hepatic (61%) MT concentrations but unaffected Zn con centrations compared with controls that consumed food ad libitum. Zn replet ion for 24 h restored intestinal and hepatic MT concentrations and reduced hepatic Zn concentration. Pair-fed control rats had elevated MT concentrati on in liver that was normalized by energy repletion. There was a significan t positive correlation between tissue Zn and MT concentrations in liver (r = 0.60, P = 0.0001), but not in small intestine. In summary, MT immunolocal ization and concentration in rat small intestine and liver were responsive to changes in Zn status, supporting the role of MT in Zn metabolism. Cell-t ype-specific localization of MT in small intestine after dietary Zn manipul ations indicates a function of Zn and MT in gut immunity and intestinal muc osal turnover, and the pattern of hepatic MT distribution with energy restr iction may be linked to detoxification processes.