Influence of fatty acid content of lysophosphatidyl choline on its myelinotoxic properties.

The efficacy of lysophosphatidyl choline (LPC) type I and type IV in producing demyelination was assessed in rat tibial and sural nerve. By light and electron microscopy, a greater myelinolytic activity was demonstrated with type I, and concomitantly electrophysiology showed a more severe conduction block. In teased nerve preparations and 1-microns thin sections, demyelinated fibres were more frequent with LPC type I. At 1 h after injection, electron microscopy showed much more extensive myelin lysis in the form of fine vesicular debris. By 6 days, completely demyelinated fibres were much more common and associated Schwann cells contained either small quantities or no myelin debris. With type IV LPC, cytopathological changes were more extensive at 1 h. A minority of Schwann cells showed swollen hydropic cytoplasm and degradation of organelles. Axonal retraction from the myelin sheath occurred in occasional fibres, and in a few unmyelinated fibres axoplasm showed organelle depletion and increased granularity. By 6 days, Schwann cells still contained large quantities of gross myelin debris and had often retracted to expose extensive areas of axolemma. The findings suggest that the two types of LPC have different myelinolytic actions, which may be related to their different fatty acid content. A possible role for the two types of LPC in 'bystander demyelination' is considered.