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I came across the MCQ in my physiology book, it says:

Erythropoietin.....

i) may decrease the life span of RBCs.

ii) is not released on breakdown of RBCs.

iii) may stimulate the stem cells.

iv) is formed mainly in liver.

v) is lipid in nature

I think ii) and iii) are correct answers, as when breaking down RBCs we don't get erythropoietin, and erythropoeitin stimulated stem cells to produce RBCs, am I right?

Because the book says that only one choice is correct. Help me please! Is there something I don't understand?

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    $\begingroup$ To simplify only a bit, EPO production is controlled by the level of oxygen in the blood. You can argue that RBC destruction causes hypoxia, but in truth, if RBC destruction does not cause hypoxia, there is no stimulus for EPO production. Like every hormone, there is more to it and more to discover. But the obvious answer is iii, and anything more is overreading. $\endgroup$ Nov 10 '17 at 16:34
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Erythropoietin is a glycoprotein cytokine (v is wrong) secreted by the kidney (iv is wrong); it stimulates erythrocyte production (erythropoiesis, from multipotent hematopoietic stem cells through erythroblasts through reticulocytes to red blood cells; iii is correct; i and ii are wrong) in the bone marrow.

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  • $\begingroup$ Why should II be incorrect? Epo stimulates the production of the RBC, when these are terminally differenciated, you should find it the anymore. $\endgroup$
    – Chris
    Nov 10 '17 at 8:11
  • $\begingroup$ @Martin Klvana, you say that erythropoietin is release when breaking down RBCs?! $\endgroup$
    – Asmaa
    Nov 10 '17 at 9:39
  • $\begingroup$ @Chris: Asmaa says only one choice is correct. $\endgroup$
    – user37894
    Nov 11 '17 at 7:23
  • $\begingroup$ @Asmaa: You say only one choice is correct. $\endgroup$
    – user37894
    Nov 11 '17 at 7:25
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    $\begingroup$ Erythropoietin can be found in mature erythrocytes. Erythropoietin inhibits apoptosis of erythrocytes by binding to erythrocytes and inhibiting erythrocyte cation channels. jasn.asnjournals.org/content/14/11/2750.long $\endgroup$
    – user37894
    Nov 11 '17 at 7:45

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