AJP - Regulatory, Integrative and Comparative Physiology, Vol 239, Issue 5 489-R496, Copyright © 1980 by American Physiological Society
Properties of body fluids influencing salt gland secretion in Pekin ducks
H. T. Hammel, C. Simon-Oppermann and E. Simon
Pekin ducks were reared and maintained on 620 mosmol NaCl/kg H2O to enhance
the secretory capability of their salt glands. When a control solution of
1,000 mosmol NaCl/kg H2O was infused intravenously at 0.2, 0.4, or 0.6
ml/min for 60-90 min, the infused loads were secreted in approximately
equal quantities, indicating that the amount of NaCl in the extracellular
fluid (ECF) before and after each infusion did not change. Salt and water
secreted in response to experimental infusions of hyposmotic saline or
blood were less than the solute and water infused. Thus, ECF volume
increased and the Na+ concentration decreased. Infusions of control
solution followed these experimental infusions. The salt and water secreted
again equaled the amounts infused, indicating that the threshold
concentration of Na+ ([Na+]th) for salt gland secretion was decreased by
the increase in ECF volume. When the colloid dextran was added to the
control solution, its infusion increased the colloid osmotic pressure of
the blood and decreased nasal secretion. Because dextran increased the
intravascular volume while the interstitial fluid volume (ISFV) decreased,
we conclude that the [Na+]th was inversely correlated with ISFV.
