Factors affecting blood viscosity in macroglobulinemic mice

Mice carrying a transplantable plasma cell tumor provide an animal model for the study of blood viscosity in macroglobulinemia. Blood viscosity was elevated and was a function of the plasma concentration of macroglobulin and of the hematocrit. The viscosity of macroglobulinemic plasma was also elevated as was the viscosity of erythrocyte suspensions which consisted of normal red cells suspended in media containing abnormal amounts of macroglobulin. The viscosity of these suspensions was a function of the viscosity of the suspending media and of the hematocrit. Macroglobulin caused aggregation of erythrocytes in vitro, and these aggregates may play a role in elevating viscosity both in vitro and in vivo. The experimental findings resemble, in many respects, observations made in human macroglobulinemia. They indicate that plasma or serum viscosity are only partial determinants of whole blood viscosity. Study of the animal model may aid in elucidating the causes of increased blood viscosity and associated symptoms in human macroglobulinemia.