Rapid Response of Protein Synthesis to Insulin in 3T3 cells: Effects of Protein Kinase C Depletion and Differences from the Response to Serum Repletion

Quiescent 3T3 cells grown in media containing 4 ~o foetal calf serum showed different
responses to insulin and to serum repletion (to 12~). Insulin stimulated protein
synthesis within 1 h and this early response was insensitive to actinomycin D. The later
insulin response showed progressive sensitivity to actinomycin D. The serum response
was slower, not occurring until 1 h, and was inhibited by actinomycin D. Depletion of
cell protein kinase C by pre-treatment with phorbol ester caused a total block of the
immediate response to insulin but had little effect on the response to serum or the later
response to insulin. Acute phorbol ester treatment stimulated protein synthesis.