Fever and changes in plasma zinc and iron concentrations in the goat: the role of leukocytic pyrogen.

In goats with trypanosomiasis (T. vivax or T. congolense) no marked fall in plasma zinc concentration was seen despite high temperature peaks, whereas plasma concentrations of iron tended to undergo some decline. In goats infected with Ehrlichia phagocytophila, there was a marked decline in plasma zinc and iron to low values on the 3rd and 4th day, respectively. Circulating endogenous pyrogen (EP) or leukocytic endogenous mediator (LEM) could not be detected in plasma from febrile goats with tick-borne fever. The intravenous injection of leukocytic pyrogen (LP) in kids caused characteristic monophasic febrile reactions, whereas no significant changes in plasma trace metals were found. So, previous evidence purporting to show that LP is similar to or may be identical with LEM is demonstrably inconclusive. Intravenous injection of E. coli lipopolysaccharide (LPS) or staphylococcal enterotoxin B (SEB) induced fever and lowering of plasma zinc and iron concentrations. The decrease in those trace metal values was more persistent in goats given SEB than in those given E. coli LPS. After intramammary infusion of SEB or E. coli LPS, fever and significant decreases in plasma zinc and iron concentrations were observed but no clear relationship was found between the temperature responses and the alterations in plasma trace metal concentrations. Furthermore, the decrease in plasma iron concentration developed more rapidly in goats given SEB than in those given E. coli LPS, whereas the decrease in plasma zinc concentrations in the former was more delayed. These data support the theory that the concentrations of zinc and iron in plasma are regulated by different mechanisms, whereas febrile reactions are mediated by another type of endogenous protein.