Differential proliferative responses of cultured Schwann cells to axolemma- and myelin-enriched fractions. I. Biochemical studies.
Cultured rat Schwann cells were treated for 72 h with axolemma- and myelin-enriched fractions prepared from rat brainstem. [3H]Thymidine was added to the cultures 48 h before the termination of the experiment. Although, both fractions produced a dose-dependent uptake of label into Schwann cells, the shape of the dose response curves and rates at which [3H]thymidine was incorporated were different. The axolemma-enriched fraction produced a sigmoid dose response curve with a Hill coefficient of 2.05. The dose response curve for myelin rose sharply and saturated at a level that was approximately 50% of the maximal response observed with axolemma. Schwann cells that had been treated with axolemma exhibited little change in the rate of [3H]thymidine incorporation from 36-72 h after the addition of the membranes. In contrast, Schwann cells accumulated label three times faster during the 48-72-h period following the addition of myelin to the cultures when compared with the rate during the preceding 12-h interval. Furthermore, the mitogenic activity of the myelin-enriched fraction was decreased by the addition of ammonium chloride, a lysosomal inhibitor, whereas the activity of the axolemmal fraction was not impaired.
D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure*; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002469:Cell Separation; D004261:DNA Replication; D007700:Kinetics; D009186:Myelin Sheath / Q000378:metabolism*; D051381:Rats; D012583:Schwann Cells / Q000166:cytology* / Q000378:metabolism; D012584:Sciatic Nerve / Q000166:cytology* / Q000378:metabolism