Intestinal Metallothionein Gene Expression and Zinc Absorption in Rats Are Zinc-Responsive but Refractory to Dexamethasone and Interleukin 1α

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Abstract
The effects of dexamethasone and interleukin 1α on intestinal metallothionein gene expression and zinc absorption were studied. Rats given parenteral zinc served as positive controls. A single intraperitoneal or intravenous dose of dexamethasone, interleukin 1α or zinc markedly increased liver metallothionein synthesis 3–9 h after injection. Intestinal metallothionein mRNA and metallothionein protein were not affected by dexamethasone or interleukin 1α, but were markedly increased by parenteral zinc. Absorption of 65Zn from isolated duodenal segments was inversely related to intestinal metallothionein concentration in rats given zinc, but was not affected by dexamethasone or interleukin 1α. Plasma zinc concentrations decreased in rats given dexamethasone or interleukin 1α and increased in those given zinc, but they were not related to 65Zn absorption. Similarly, multiple intraperitoneal administration of either dexamethasone or interleukin 1α, or oral administration of dexamethasone, for 7 d markedly increased liver metallothionein synthesis but did not affect intestinal metallothionein concentration or 65Zn absorption. These results suggest that intestinal metallothionein gene expression and 65Zn absorption are refractory to glucocorticoid hormone and interleukin 1α.