High uptake and rapid metabolism of palmitate in peripheral nerves of normal and Trembler mice in vivo: Similarities and differences.
In vivo, short-term palmitate metabolism was studied in normal and Trembler mouse sciatic nerves, after intraneural injection of 6.34 pmol of [(3)H]palmitate. After 30 min of in vivo incubation, all the [(3)H]palmitate available for short-term lipid metabolism (90% of the injected substrate) had already been used up in both normal and Trembler sciatic nerves. Despite the normal metabolic level of the [(3)H]palmitate, the distribution of the label between the various polar lipids was abnormal in the mutant's nerves: sphingomyelin and phosphatidylcholine were more labelled than in normal nerves, while the other lipids, and particularly the cerebrosides, were less labelled. The labelled fatty acid distribution in four polar lipids, purified by thin-layer chromatography, was also abnormal, correlating with a decreased overall [(3)H]palmitate elongation (after 2 h, normal = 44%, Trembler = 24%), and a severely decreased synthesis (5- to 10-fold) of saturated very long-chain fatty acids. In normal nerves, saturated very long-chain fatty acids represented about 8% of the total labelled fatty acids and they were preferentially incorporated into the cerebrosides. The rapid depletion of the [(3)H]palmitate, the high level of its incorporation into polar lipids of both normal and Trembler mouse sciatic nerves and the excellent reproducibility of the results, have led us to propose a novel "pulsed wave" method for the in vivo study of intracellular lipid transport phenomena implicated in peripheral nerve myelin assembly.
Heape
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Laboratoire de Biogenése Membranaire, Institut de Biochimie Cellulaire et Neurochimie du CNRS, 1 rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France.
Boiron
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Cassagne
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