Compartmental analysis of circulation of erythrocytes through the rat spleen

Control, polycythemic, and anemic spleens of Sprague-Dawley rats surgically removed under pentobarbital sodium anesthesia (0.06 mg/g ip) were perfused in vitro by methods similar to those reported by Song and Groom (Am. J. Physiol. 220: 779-784, 1971). Red Blood cell (RBC) washout curves obtained for each group could be described adequately by a series of three exponentials--fast, intermediate, and slow--representing functional compartments in the spleens. Best-fit estimates of the parameters were used to characterize the flow distributions, cellular capacities, and t1/2 for washout of these components. It is thought that the fast compartment represents flow through intrasplenic vessels (including shunts) that bypass the red pulp, the intermediate compartment represents RBCs that flow through less impeded passageways in the red pulp, and the slow compartment consists of more tortuous, convoluted pathways through the red pulp. During polycythemia and anemia, inflow to the intermediate component was decreased, which suggested decreased filtration. In the slow compartment, the shutdown during polycythemia suggested RBC storage whereas during anemia control levels of inflow but increased t1/2 for washout suggested sequestration or erythropoiesis.