ACUTE-PHASE HYPOFERREMIC RESPONSE TO LIPOPOLYSACCHARIDE IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

1. Iron concentrations in the plasma of rainbow trout, Oncorhynchus mykiss, decreased after the fist were injected i.p. with lipopolysaccharides (LPS) from smooth and rough strains of two species of Gram-negative bacteria. The total iron-binding capacity of the blood was unchanged after LPS injection. 2. Transferrin saturation (estimated as plasma iron x 100/total iron-binding capacity) was 20-38% in uninjected and saline-injected fish, decreasing to 8-18% 24 hr after injection of 1 mg/kg LPS. 3. Plasma iron concentrations were lowest at 48-72 hr after i.v. LPS administration, returning to normal concentrations by 96-120 hr. 4. The minimum LPS dose inducing significant hypoferremia in rainbow trout was 10-mu-g/kg. This is a lower dose than is required for induction of hypoferremia in some endothermic species.