AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 6 1449-R1453, Copyright © 1994 by American Physiological Society
Plasma volume conservation in pigeons: effects of air temperature during dehydration
N. Carmi, B. Pinshow and M. Horowitz
Mitrani Center for Desert Ecology, Jacob Blaustein Institute for Desert Research, Sede-Boqer, Israel.
We assessed the effects of the ambient air temperature prevailing during
dehydration, which included complete water and food deprivation, on plasma
volume (PV) conservation in pigeons (Columba livia) exposed to air
temperatures of 25 degrees C (n = 7), 36 degrees C (n = 12), and 40 degrees
C (n = 24). The pigeons were dehydrated for 65.4, 32.3, and 27.7 h, on
average, at 25, 36, and 40 degrees C, respectively. Dehydration rates
averaged 5, 10, and 15.2% of initial total body water (TBW) per day at the
three air temperatures, in ascending order. Birds exposed to 25 and 36
degrees C maintained PV despite the fact that they lost, on average, 14 and
17.3% of their TBW, respectively. In contrast, PV in pigeons exposed to 40
degrees C decreased by 8.9%, even though the reduction in TBW (17.7%) was
similar to that incurred at 36 degrees C. Mean plasma osmolalities reached
347.7, 345.6, and 374.8 mosmol/kgH2O at 25, 36, and 40 degrees C,
respectively. No significant changes occurred in hematocrit (Hct) and
hemoglobin concentrations (Hb) during dehydration at 25 and 36 degrees C.
However, at 40 degrees C Hb increased by 8.2% with no change in Hct,
indicating a decrease in red blood cell volume (RBCV). The results of this
study suggest that maintenance of PV and RBCV is affected not only by the
dehydration level attained but also by the ambient conditions under which
dehydration is induced and the rate at which dehydration takes place.
