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Am J Physiol Regul Integr Comp Physiol 257: R377-R382, 1989;
0363-6119/89 $5.00
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AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 2 377-R382, Copyright © 1989 by American Physiological Society

ARTICLES

Osmoregulation and body fluid compartmentalization in dehydrated heat-exposed pigeons

Z. Arad, M. Horowitz, U. Eylath and J. Marder
Department of Biology, Technion-Israel Institute of Technology, Haifa.

Osmoregulatory and volume-regulatory responses of heat-acclimated pigeons (Columba livia) were studied during normal hydration and dehydration combined with heat exposure. Dehydrated heat-exposed pigeons (exposure to 50 degrees C following 48 h of water deprivation; 16-18% mass loss) could recover 97% of their initial body mass within 30 min of free drinking at the end of heat exposure. At the end of heat exposure, body temperature increased by 3 degrees C and hematocrit increased by 12.5%. Serum electrolyte and protein concentrations increased by 33-53% (P less than 0.001). Serum osmolality reached an outstanding mean value of 436.7 +/- 28.5 mosmol/kg (n = 11), 30.5% higher than the normal mean value. Serum glutamic-pyruvic transaminase and glutamic-oxaloacetic transaminase concentrations did not change during dehydration, suggesting no impairment in circulatory function. Blood urea nitrogen increased sixfold, indicating a total shutdown of the kidney. Relative plasma volume was maintained during dehydration at the expense of extravascular spaces and with a decreased vascular permeability as indicated by the increase in Evans blue-labeled albumin half-life (control, 104 +/- 53 min; dehydration, approaching infinity). Altogether, extracellular fluid volume and intracellular fluid volume contributed 53 and 47% of the evaporative water loss, respectively. It is concluded that plasma volume regulation may play an important role in the effective thermoregulatory responses of heat-exposed dehydrated pigeons. This regulation is achieved by preferential shifts of body water reserves among the various body water compartments coinciding with a remarkable tolerance to high osmotic pressures.


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E. Ophir, Y. Arieli, J. Marder, and M. Horowitz
Cutaneous blood flow in the pigeon Columba livia: its possible relevance to cutaneous water evaporation
J. Exp. Biol., September 1, 2002; 205(17): 2627 - 2636.
[Abstract] [Full Text] [PDF]


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