Protein synthesis during oxygen conformance and severe hypoxia in the mouse muscle cell line C2C12.

Oxygen conformance can be described as the ability to reduce energy demand, and hence oxygen consumption, in response to a decline in oxygen availability without a decrease in the concentration of ATP. It has been proposed that oxygen conformance may enhance cellular survival at low oxygen concentrations. We demonstrate that non-contracting C2C12 cells, a mouse skeletal muscle cell line, are capable of oxygen conformance. Typically, we found oxygen consumption to decline by 30-40% as the concentration of oxygen was reduced from 100 microM to 10 microM. Unexpectedly, the rate of protein synthesis, a major energy consumer in the cell, did not decrease significantly during oxygen conformance. Unlike oxygen conformance, severe hypoxia (<0.5 microM) caused a 36% decline in the concentration of PCr, and under these conditions of energy stress, the rate of protein synthesis declined by 43%. We conclude that there are two distinct metabolic responses to declines in oxygen concentration in non-contracting C2C12 cells.