Erythropoietin is secreted by ?

Ans. is `d' i.e., KidneyErythropoitin Erythropoietin is a glycoprotein hormone which stimulate erythrocyte production. Erythropoietin increases the number of erythropoietin sensitive committed stem cells in the bone marrow that are conveed to red blood cells precursors and subsequently to mature erythrocytes. In the absence of erythropoietin, erythroid stem cellsundergo apoptosis.In adults, about 85% of erythropoietin comes from the kidney (interstitial cells in peritubular capillary bed) and 15% from liver (Perivenous hepatocytes). Small amount is also produced in brain; and uterus and oviducts. Ceain tumors also produce erythropoietin, .e.g., Renal cell carcinoma, Hepatoma and cerebellar hemangioblastoma.The most impoant stimulus for erythropoietin secretion is hypoxia. Other stimulus that can increase its secretion are cobalt salts, androgens, alkalosis due to high altitude, and catecholamines f3-adrenergic mechanism.Pregnancy (due to placental lactogen), testosterone and prolactin increase the activity of erythropoietin. Estrogen inhibits utilization of erythropoietin by marrow cells and also impairs its production. Progesterone increase the effect of erythropoietin by enhancing the effect of placental lactogen and by antagonizing the effect of estrogen.