INTESTINAL METALLOTHIONEIN GENE-EXPRESSION AND ZINC-ABSORPTION IN RATS ARE ZINC-RESPONSIVE BUT REFRACTORY TO DEXAMETHASONE AND INTERLEUKIN 1-ALPHA

The effects of dexamethasone and interleukin 1-alpha 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 1-alpha 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 1-alpha, but were markedly increased by parenteral zinc. Absorption of Zn-65 from isolated duodenal segments was inversely related to intestinal metallothionein concentration in rats given zinc, but was not affected by dexamethasone or interleukin 1-alpha. Plasma zinc concentrations decreased in rats given dexamethasone or interleukin 1-alpha and increased in those given zinc, but they were not related to Zn-65 absorption. Similarly, multiple intraperitoneal administration of either dexamethasone or interleukin 1-alpha, or oral administration of dexamethasone, for 7 d markedly increased liver metallothionein synthesis but did not affect intestinal metallothionein concentration or Zn-65 absorption. These results suggest that intestinal metallothionein gene expression and Zn-65 absorption are refractory to glucocorticoid hormone and interleukin 1-alpha.