Mixing of Labeled Erythrocytes in the Dog's Spleen

¹ From the Departments of Physiology and Pharmacology, University of Texas, Dental Branch, and Baylor University College of Medicine, Houston, Texas

Dogs anesthetized with morphine-pentobarbital were injected with Cr⁵¹-tagged red cells, and their mixing time in the general circulation and the spleen was compared. The necessary blood samples were taken and the spleens rapidly excised at 10, 20 or 30 minutes after the injection of the tagged red cells. When the data were grouped according to the size of the spleen and irrespective of the time of removal, the mixing of tagged red cells in small spleens was practically the same as in the general circulation. With increasing sizes of spleens the mixing appeared to be progressively less complete than in the general circulation. If the spleen size was disregarded and the data grouped according to the time after the injections of tagged red cells mixing in the spleen was still incomplete after 30 minutes. However, the maximum mean possible error that could be introduced into the determination of total red cell volume if all the unmixed red cells were ejected into the general circulation would be less than 5% at the 20-minute period.