Internodal distribution of phosphatidylcholine biosynthetic activity in teased peripheral nerve fibres: an autoradiographic study.

Radioactive choline injected into mouse sciatic nerve is rapidly incorporated into into phosphatidylcholine. Sites of deposition of this phospholipid have been localized along the internode in autoradiography prepared from individually teased fibres. The newly synthesized lecithin formed during 20 min or 2 h labelling periods is concentrated in the perinuclear region of the Schwann cell and in strands radiating from this portion of the cell. This labelling pattern, representing a complex of enzyme activities, is distributed in a similar, though not identical, fashion to that of Schwann cell mitochondria as localized by histochemical methods. These findings suggest that soluble and membrane-associated enzymes required for phosphatidylcholine formation are distributed in Schwann cell cytoplasm along superficial longitudinally oriented channels as depicted in recent freeze-fracture studies.