Role of the spleen in determining total body hematocrit

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Abstract
Plasma volumes were measured by T-1824 and cell volumes by Cr51-tagged cells in intact and acutely splenectomized dogs. The blood activity level reached a nearly constant value by about 20 minutes in intact, and 10 minutes in splenectomized dogs. Splenic contraction produced a rise in arterial hematocrit and in activity, but no significant change in the calculated total red cell volume. This indicates that the tagged cells reached an equilibrium concentration in the spleen fairly rapidly. The ratio of total body hematocrit to arterial hematocrit was quite variable between animals. The average for intact dogs was 1.021. After splenic contraction, their ratio was lowered to 0.838. The lowered value persisted for at least 40 days after splenectomy, despite a frequently severe decrease in red cell volume. Due to the variation between animals, the actual value of the ratio has no clear significance. Successive estimations of cell volume in dogs under control conditions showed a standard deviation of 6.4%.