The
enzyme activities of
ceramide galactosyltransferase and
ceramide glucosyltransferase were assayed as a function of time (0, 1, 2, 4, 7, 14, 21, 28, and 35 days) after
crush injury or permanent transection of the adult rat sciatic nerve. These experimental models of neuropathy are characterized by the presence and absence of axonal regeneration and subsequent myelin assembly. Within the first 4 days after both
injuries, a 50% reduction of
ceramide galactosyltransferase-specific activity was observed compared to values found in the normal adult nerve. This activity remained unchanged at 7 days after injury; however, by 14 days the
ceramide galactosyltransferase activity diverged in the two models. The activity increased in the crushed nerve and reached control values by 21 days, whereas a further decrease was observed in the transected nerve such that the activity was nearly immeasurable by 35 days. In contrast, the
ceramide glucosyltransferase activity showed a rapid increase between 1 and 4 days, followed by a plateau that was 3.4-fold greater than that in the normal adult nerve, which persisted throughout the observation period in both the crush and transection models. [3H]
Galactose precursor incorporation studies at 7, 14, 21, and 35 days after injury confirmed the previously observed shift in biosynthesis from the
galactocerebrosides during myelin assembly in the crush model to the
glucocerebrosides and oligohexosylceramide homologues in the absence of myelin assembly in the transection model. The transected nerves were characterized by a peak of biosynthesis of the
glucocerebrosides at 14 days. Of particular interest is the biosynthesis of the
glucocerebrosides and the oligohexosylceramides at 7 and 14 days after
crush injury.(ABSTRACT TRUNCATED AT 250 WORDS)