SPHINGOMYELIN IS SYNTHESIZED AT THE PLASMA-MEMBRANE OF OLIGODENDROCYTES AND BY PURIFIED MYELIN MEMBRANES - A STUDY WITH FLUORESCENT AND RADIOLABELED CERAMIDE ANALOGS

In most cell types sphingomyelin is synthesized predominantly in the c is-medial compartments of the Golgi stacks whereas the contribution of the plasma membrane is much lower. The aim of this study was to asses s the contribution of both compartments to the synthesis of sphingomye lin in myelinating cells. Therefore, oligodendrocytes from rat spinal cord were incubated in culture with fluorescently- or radiolabelled ce ramides, and the effects of a block in the vesicular flow (monensin, b refeldin A, low temperature) on surface synthesis of sphingomyelin wer e evaluated. The results indicate that approximate to 50% of the sphin gomyelin synthase is present at the plasma and myelin membranes of oli godendrocytes.