Antidiuretic hormone and angiotensin II plasma concentrations in febrile Pekin ducks

Abstract

1. The objective of this study was to determine the changes in plasma concentrations of the hormones arginine vasotocin (AVT) and angiotensin II (AII) associated with lipopolysaccharide (LPS)-induced fever in Pekin ducks. 2. LPS, intravenously administered into conscious birds at doses of 1, 10 and 100 microgram kg-1, caused dose-dependent and monophasic increases in body temperature, with fever index values of 3.5, 7.0 and 10.6, respectively. 3. Plasma AVT concentrations also increased with 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 caused by the highest dose of LPS. 4. Plasma AII concentrations did not significantly change from basal values (mean of 45.5 +/- 6.3 pg ml-1 for all groups) during the acute phase of the fever response. 5. The osmotic status of the birds, as indicated by plasma osmolality and electrolyte values, did not significantly change in any of the experimental 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.

Figure 1. LPS-induced changes in body temperature, AVT and AII concentrations

Body temperature (A), plasma AVT concentration (B) and plasma AII concentration (C) responses to the i.v. administration of saline (○) or LPS at doses of 1 (□), 10 (⋄) and 100 μg kg⁻¹ (▵) in 7 conscious Pekin ducks. For the LPS doses of 1 and 10 μg kg⁻¹ plasma AVT concentrations increased, in comparison with birds receiving saline, at about 12.00 h, but this difference only became significant at 16.00 h. With LPS given at the dose of 100 μg kg⁻¹, plasma AVT levels increased significantly above those for saline at 12.00 h and remained significantly greater than saline values for the duration of the experiment. At 16.00 h the plasma AVT levels associated with the LPS at 100 μg kg⁻¹ were significantly higher than those in birds given LPS doses of 1 and 10 μg kg⁻¹.

Figure 2. Correlation between plasma AVT concentration and body temperature

Relationship between plasma AVT concentration and body temperature in 7 conscious Pekin ducks given intravenous saline (○) or LPS at doses of 1 (□), 10 (⋄) and 100 μg kg⁻¹ (▵). Each point is the mean value for the birds at each of the 7 sample times. r = 0.84, n = 28, P < 0.0001.