Interleukin 1-induced depression of iron and zinc: role of granulocytes and lactoferrin.

The mechanism(s) of stress-induced hypoferremia and hypozincemia remains unclear. We studied the role of granulocytes and lactoferrin (LF) in endotoxin and murine interleukin 1 (IL-1)-induced depression of serum Fe and Zn concentrations in both rabbits and rats. Both endotoxin and IL-1 administration induced significant hypoferremia (P less than 0.01) and hypozincemia (P less than 0.01) after 6 h in both species. Granulocyte depletion before IL-1 infusion significantly (P less than 0.01) diminished the hypoferremia but not the hypozincemia. Moreover, infusion of 5 or 15 mg of human LF into rabbits caused significant hypoferremia (P less than 0.005) without hypozincemia. Significant hypozincemia (P less than 0.01) could only be demonstrated after a 75-mg infusion. In contrast, infusions of human transferrin at equivalent doses (5, 15, and 75 mg) induced neither hypoferremia nor hypozincemia. Therefore endotoxin and IL-1-induced hypoferremia and, to a much lesser degree, hypozincemia are granulocyte dependent. Granulocyte released LF is a specific carrier molecule for transport and removal of Fe from the circulation during the acute phase response. The data suggest a mechanistic dissociation of IL-1-induced hypoferremia and hypozincemia with LF-independent mechanisms for Zn.