Conservation of blood plasma fluids in hamadryas baboons after thermal dehydration.

After 2 days of water deprivation in a warm climate, Papio hamadryas baboons lost 10% of their body mass, 12.5% of their total body water (3H2O) space, but only 4% of their plasma volume [Evans blue (EB) space]. Hematocrit and hemoglobin concentration as well as blood viscosity and blood pressure were not affected by thermal dehydration. Plasma colloid osmotic pressure (COP) in the dehydrated animals was, however, 8 Torr higher than in fully hydrated baboons. Total mass and concentration of plasma albumin, and protein concentration increased after dehydration. Both half times (T 1/2) of EB and T 1/2 of 131I-serum albumin were twice as high as in the dehydrated animal than in the fully hydrated ones. Incorporation rate of L-[3H]leucine in the plasma proteins was similarly higher in the dehydrated animals. The capacity of the P. hamadryas baboon to maintain its plasma volume at the expense of losses from other body fluid compartments is related to an increase in the blood COP that is brought about by a more efficient retention of albumin and an increase in its rate of synthesis.