Conversion of labelled cerebrosides in adult rabbit brain, local brain necrosis, autolysis series and in brain homogenate

Summary

Tetracosanoic-(15,16-³H) acid was used to form lignoceroyl psychosine (kerasin). Emulsion of the labelled sphingolipid was injected directly into the brain of adult rabbits and the resultant metabolic products were examined for radioactivity over a period of 21 days. In six animals the precursor was administered after application of cold on the exposed dura. This procedure was found to be an easy practical method for inducing local brain necrosis which resembled histologically and biochemically sudanophilic myelin breakdown occurring in some demyelinating diseases. Small amounts of the labelled material were used in an autolysis series and in an in-vitro study with brain homogenate.

The radiochemical investigation revealed that most of the applied cerebroside remained unchanged. Some radioactivity was found in the ester linked fatty acids (glycerophospholipids and neutral fats), whose chains shortened with time down to acids with chain lengths of C 16 and C 18. Only very small amounts of kerasin were directly converted to sulphatides or via ceramide to sphingomyelin.

The suprising finding that the major portion of initially administered linked labelled fatty acid was detectable in neutral fats in undamaged brains after 2 days and the poor degradation of exogeneous applied kerasin was not increased by the intervention of artificially induced macrophages leads to the suggestion that the hydrophobic material was not able to enter oligodendroglia cells which are responsible for the metabolism of myelin cerebrosides.

No degradation products were seen in the autolysis series or after incubation with brain homogenate.