Dog red blood cells. Adjustment of density in vivo.

Red blood cells from mature dogs contain less Na and more K than would be the case if they were in Donnan equilibrium with plasma. They have no ouabain-sensitive Na pump, and their membranes are deficient in Na, K-ATPase. Experiments are reported in which dog red cells were first loaded with supranormal quantities of Na and water and then reinjected into the dog. Over the course of 26-40 h the Na- and water-loaded cells returned to a normal state of hydration as judged by their density. It is concluded that dog red cells possess some means of correcting their swollen status in vivo, despite their lack of a ouabain-sensitive cation transport apparatus.