Figure 6.

EPO production in the C2C12 and primary myoblast cultures from TgEpoR, tg6, and WT mice. A, B) Quantitative real-time RT-PCR of mouse EPO mRNA expression under 21% O₂ (left panel) or 5% O₂ (right panel) for C2C12 cell cultures without (A) and with (B) EPO treatment (5 U/ml); β-actin mRNA expression was used as the internal control. C) EPO expression was determined for primary myoblasts isolated from WT and TgEpoR mice at 21% O₂, as well as the induction of EPO expression at reduced oxygen tension (5% O₂). D) Expression of endogenous mouse EPO (mEPO) and human tgEPO was determined for primary myoblasts isolated from tg6 mice at 21% O₂, as well as the induction of transgenic and endogenous EPO expression at reduced oxygen tension (5% O₂). E) EPO activity in conditioned medium from C2C12 cells cultured at 21% O₂ (squares) and 5% O₂ (diamonds) was determined by an EPO bioassay. Cell culture supernatants were collected at different time points (d 0, 1, 2, 3). F) Primary myoblasts isolated from WT mice (solid circles; dashed line), tg6 mice (open circles; solid line) and TgEpoR mice (open triangles; solid line) were cultured. EPO bioactivity at 21% O₂ and EPO induction at 5% O₂ were determined in conditioned medium harvested at d 0, 1, 2, and 3. *P < 0.05.