ANTIDIURETIC-HORMONE AND ANGIOTENSIN-II PLASMA-CONCENTRATIONS IN FEBRILE PEKIN DUCKS

1. The objective of this study was to determine the changes in plasma concentrations of the hormones arginine vasotocin (AVT) and angiotensi n II (AII) associated with lipopolysaccharide (LPS)-induced fever in P ekin ducks. 2. LPS, intravenously administered into conscious birds at doses of 1, 10 and 100 mu g kg(-1) caused dose-dependent and monophas ic increases in body temperature, with fever index values of 3.5, 7.0 and 10.6, respectively. 3. Plasma AVT concentrations also increased wi th the progression of the fever, with the largest elevation (from 8.4 +/- 1.6 to 25.2 +/- 3.2 pg ml(-1); means +/- S.E.M., n = 7) being caus ed by the highest dose of LPS. 4. Plasma AII concentrations did not si gnificantly change from basal values (mean of 45.5 +/- 6.3 pg ml(-1) f or all groups) during the acute phase of the fever response. 5. The os motic status of the birds, as indicated by plasma, osmolality and elec trolyte values, did not significantly change in any of the experimenta l animals. 6. The elevation of AVT in avian fever leads to speculation about a possible antipyretic action of this hormone, which would have particular relevance to understanding the evolution of fever.