The synthesis and turnover of ferritin in rat L-6 cells. Rates and response to iron, actinomycin D, and desferrioxamine.

Rates of ferritin accumulation in the L-6 line of rat skeletal myoblasts cultured in the presence of ferric nitrilotriacetate (FeNTA) were measured and found to vary with the extracellular concentration of FeNTA as predicted from dose response experiments. The rate of ferritin accumulation is constant for up to 92 h in these cells after addition of iron, with the exception of the first few hours of synthesis in which the rate is approximately twice that observed at later times. Experiments in which the specific activity of newly synthesized ferritin was calculated implied that the rate of ferritin degradation might be higher in this earlier period as well; pulse-chase experiments confirmed this hypothesis. Ferritin synthesis is thought to be induced by iron in the absence of RNA synthesis. Accordingly, actinomycin D was shown not to inhibit the synthesis of ferritin in response to FeNTA. Rather, a pronounced stimulation of the synthetic rate was observed. Finally, desferrioxamine was shown both to decrease the rate of ferritin synthesis and increase its rate of degradation. Possible mechanisms for these phenomena are discussed.