Comparison of distribution spaces for labeled and unlabeled cells and plasma in dogs

¹ Department of Physiology, University of Louisville School of Medicine, Louisville, Kentucky

Distribution spaces for T-1824 (PVl) and for P³²-labeled red cells (CVl) were determined in intact barbitalized dogs by conventional methods. One hour after injection of these two labels, their circulating concentrations were reduced by a paced simultaneous infusion of a large volume of unlabeled autologous whole blood, and withdrawal of an equal volume from the circulation. Distribution spaces were calculated from the decrease in the respective label concentrations, for the infused unlabeled plasma (PVd) and unlabeled cells (CVd). When corrections were made for external volume changes due to sampling, PVl was in good agreement with PVd, and CVl with CVd. When donor blood was substituted for autologous blood in this procedure, agreement was usually not observed. When blood volume was expanded by infusing autologous blood without preliminary or simultaneous withdrawal, CVd agreed with CVl, but large differences were observed between PVd and PVl. The two plasma values were brought into somewhat better, though not complete, agreement by preliminary withdrawal, but CVd was usually made less than CVl.