96. An 20-year-old man moves from sea level to an elevation of 2,600 m to train as a skier. The increased requirement for oxygen delivery to tissues at the higher elevation stimulates the synthesis of a renal hormone (erythropoietin), which targets hematopoietic stem cells in the bone marrow. Erythropoietin promotes the survival of early erythroid progenitor cells primarily through which of the following mechanisms?
|A.||Altered cell-matrix adhesion|
Downregulation of p53
Enhanced glucose uptake
Inhibition of apoptosis
Answer: D Inhibition of apoptosis
Recent studies indicate that erythropoietin promotes the survival of early erythroid progenitor cells through an inhibition of the default apoptosis pathway.
Thus, this hormone rescues stem cells that are otherwise fated to undergo programmed cell death. None of the other choices are known to control the expansion of hematopoietic stem cell colonies in the bone marrow.