Red blood cells The fundamental stimulus for production of red blood celf( erythropoiesis) is erythropoietin(红细胞生成素), a glycoprotein produced by the kidneys in response to renal tissue hypoxia. Other hormones, such as corticosteroids, thyroid hormone and androgens stimulate the production or release of erythropoietin but have no intrinsic erythropoietic activity. The average lifespan of a circulating erythrocyte is 110 120 days in the dog and 68 days in the cat. Aged or damaged red cells are removed primarily by macrophages in the liver, spleen and bone marrow.Red blood cells The fundamental stimulus for production of red blood cells (erythropoiesis) is erythropoietin(红细胞生成素）, a glycoprotein produced by the kidneys in response to renal tissue hypoxia. Other hormones, such as corticosteroids, thyroid hormone and androgens, stimulate the production or release of erythropoietin but have no intrinsic erythropoietic activity. The average lifespan of a circulating erythrocyte is 110- 120 days in the dog and 68 days in the cat. Aged or damaged red cells are removed primarily by macrophages in the liver, spleen and bone marrow