Metabolism of peripheral nerve monogalactosylceramides.
The metabolism of hydroxy galactocerebrosides (GalCe-OH) and nonhydroxy galactocerebrosides (GalCe) was investigated during nerve development, degeneration and regeneration by endoneurial injection of [14C]acetate and by in vitro incubation of rat sciatic endoneurium with [14C]acetate, [3H]galactose or [3H]glucose. After endoneurial microinjection, [14C]acetate was found to be incorporated first into GalCe-OH and later, and to a much lesser degree, into GalCe. The ratio of 14C-labeled GalCe-OH to GalCe decreased with time and remained fairly constant after 4 hr. On the other hand, in vitro incorporation of [14C]acetate resulted in higher 14C-labeling in GalCe and monogalactosyl diacylglycerol (MGDG) and lower 14C-labeling in GalCe-OH, diminishing with incubation time. After 24 hr, only GalCe and MGDG were labeled. When [3H]galactose or [3H]glucose, instead of [14C]acetate, were used as precursor in vitro, a similar preference for labeling of GalCe-OH was demonstrated in regenerating nerve. These data suggest that hydroxy fatty acids and hydroxy ceramides are the preferred substrates in peripheral nervous system for the sphingosine acyltransferase and the UDP-galactose:ceramide galactosyltransferase reactions, respectively. The alpha-hydroxylation system did not appear to be fully functional under in vitro conditions. The biosynthesis of GalCe-OH was greatly enhanced during nerve fiber regeneration and decreased rapidly with increasing age. This suggests that a close interrelation exists between alpha-hydroxylation and peripheral nerve myelination.
Yao
J K
JK
Department of Veterans Affairs Medical Center, Pittsburgh, Pennsylvania 15206.
D000085:Acetates / Q000378:metabolism; D000818:Animals; D002554:Cerebrosides / Q000378:metabolism*; D005690:Galactose / Q000378:metabolism; D005699:Galactosylceramides / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D008845:Microinjections; D009409:Nerve Crush; D009410:Nerve Degeneration / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology; D010525:Peripheral Nerves / Q000254:growth & development / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D000085:Acetates; D002554:Cerebrosides; D005699:Galactosylceramides; D005690:Galactose