BLOOD-VISCOSITY IN CHRONICALLY HYPOXIC RATS - AN EFFECT INDEPENDENT OF PACKED CELL-VOLUME

We compared apparent blood viscosity, measured with a cone-plate visco meter, in normoxic and chronically hypoxic rats. All comparisons were made at equal packed cell volume (PCV) and shear rate conditions. Appa rent viscosity of whole blood from the hypoxic rats was significantly lower than that from normoxic littermates and was similar to that of y oung rats. Apparent viscosity of red cells from hypoxic rats suspended in phosphate buffered saline remained lower than that from the normox ic rats. When blood cells from the hypoxic rats were suspended in plas ma from normoxic rats, apparent viscosity was lower than when blood ce lls from normoxic animals were suspended in plasma from hypoxic rats. The lower viscosity of the blood from hypoxic rats appears to be assoc iated with characterstics present in newly generated red cells. The re duced apparent viscosity of blood in hypoxic rats may partially compen sate for the increase in PCV, at least during the early stages of hypo xia.