Myelin protein metabolism in demyelination and remyelination in the sciatic nerve

Lysophosphatidylcholine (LPC) was injected intraneurally into the right sciatic nerve of a series of rats, leaving the left nerve as a control. At various time points up to 30 days after LPC treatment, the injected and control nerves were removed and incubated with [3H]amino acids, then purified myelin was prepared from the nerves. At all time points investigated the uptake of labeled amino acids was much higher in myelin proteins from the LPC-treated nerve than in those from the intact control nerve. [3H]Fucose uptake was also slightly increased. In the first week after LPC injection the increased amino acid incorporation was much greater in the myelin proteins of molecular weight higher than P0. From 10 days on, the smaller myelin proteins including P0, 19K, P1 and P2 showed the largest increase. From comparison of the morphology and biochemistry at 3 and 7 days after LPC injection, we propose that in the first 7 days, while myelin is degenerating, those proteins associated with Schwann cell or myelin reaction, interaction, and recognition functions are most stimulated metabolically, while after ten days the structural myelin proteins are actively resynthesized and the axon is remyelinated.