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Saline-Infusion-Induced Increases in Plasma Osmolality Do Not Stimulate Nasal Gland Secretion in the Ostrich (Struthio camelus)

David A. Gray and Christopher R. Brown
Physiological Zoology
Vol. 68, No. 1 (Jan. - Feb., 1995), pp. 164-175
Stable URL: http://www.jstor.org/stable/30163924
Page Count: 12
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Saline-Infusion-Induced Increases in Plasma Osmolality Do Not Stimulate Nasal Gland Secretion in the Ostrich (Struthio camelus)
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Abstract

Nasal gland activity was monitored in five freshwater and five saltwater-acclimated adult ostriches given an intravenous infusion of 1,500 mosm/kg sodium chloride for 90 min at 5 mL/min. The hyperosmotic infusion increased the plasma osmolality from 303.4 ± 6.9 to 353.3 ± 13.1 mosm/kg in the freshwater birds and from 299.4 ± 16.2 to 328.8 ± 15.4 mosm/kg in the saltwater-acclimated animals. None of the freshwater ostriches produced any observable nasal secretion. Two of the saltwater birds did show signs of glandular activity, but this was of short duration (5-10 min) and yielded insignificant volumes of fluid. The nasal glands of ostriches do not appear to play a quantitatively important role in the elimination of the administered saline load. Changes in plasma concentrations of arginine vasotocin (AVT) in response to the hyperosmotic infusion were also determined. Plasma AVT levels increased in parallel with the elevations in plasma osmolality (from 5.4 ± 0.9 to 19.4 ± 8.6 pg/mL in the freshwater ostriches and from 7.7 ± 4.2 to 16.7 ± 6.0 pg/mL in the saltwater-acclimated birds). The correlations between plasma osmolality and plasma AVT indicated osmotic sensitivities for AVT release of 0.25 and 0.21 pg/mL per mosm/kg in the freshwater and saltwater birds, respectively. These values are similar to those found in other avian species, which suggests that an enhanced sensitivity for AVT release is not a means by which ostriches cope with osmotic stress.

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