Blood volume and plasma constituent changes in splenectomized dogs consequent to exercise.

To assess the effects of submaximal exercise on fluid balance and blood constituents, changes in plasma volume, hematocrit, hemoglobin, plasma protein, serum osmolality, and serum electrolytes were measured in splenectomized dogs during treadmill work and recovery. During exercise approximating 32 and 50% of Vo2max, plasma volume did not significantly change. During recovery, plasma volume tended to increase by the same amount at both levels of exercise. Both total circulating plasma protein content and protein concentration increased during exercise. Serum osmolality increased abruptly during exercise and returned to the pre-exercise level immediately after cessation of work. Plasma volume changes calculated from both hematocrit and hemoglobin concentrations correlated well with direct measurements using labelled erythrocytes, but values calculated from hematocrit alone averaged 12% higher.