Glycoproteins and proteins in an axolemma‐enriched fraction and myelin from developing rats: Effect of maternal ethanol consumption

Abstract

The present study examined proteins and glycoproteins from an axolemma-enriched fraction from the developing offspring of female rats that were pair-fed control or 6.6% (50 g/liter) ethanol liquid diets on a chronic basis prior to parturition. In addition, this study examined the synthesis of the major CNS myelin-associated glycoprotein (MAG) as an index of myelin maturation. The results of the latter study demonstrated normal MAG maturation in ethanol-treated rats. However, a significant decrease in the proportion of radioactivity associated with MAG was found in the developing offspring of ethanol-treated rats. The major axolemmal proteins from 32-day rats included those with molecular weights of 105 K, 81 K, 62 K, 55 K, 52 K, 36 K, and 33 K. Major peaks of radioactivity were associated with fucosylated axolemmal glycoproteins with apparent molecular weights of 150 K, 130 K, 85 K, 76 K, and 64 K. Several development-related changes in the protein composition of axolemma-enriched fractions were observed in control animals. Between 22 and 32 days of age control rats exhibited a significant (P less than .05) decrease in the proportion of axolemmal proteins that had apparent molecular weights of 150 K, 105 K, and 62 K. A development-related decrease in the 105 K axolemma-associated protein did not occur during the 22-32 day age period in the offspring of ethanol-treated animals. At 22 days the proportion of this 105 K protein in affected offspring was significantly (P less than .05) less than that in age-matched control rats and comparable to that in 32-day control rats. The relative distribution of radioactivity among fucosylated axolemmal glycoproteins also changed significantly between 22 and 32 days of age. These changes include a decrease in the proportion of radioactivity associated with the 110 K, 55 K, and 52 K fucosylated glycoproteins and an increase in the proportion of radioactivity associated with the 85 K and 67 K glycoproteins. Several small, but significant (P less than .05) alterations were found associated with glycoproteins in an axolemma-enriched fraction from 22- and 32-day ethanol-treated rats.

Effects of Ethanol Exposure on Myelination and Axon Numbers in the L2 Dorsal Root of the Neonatal Rat

“…However, Bass and Volpe [7], using primary cultures of cerebral glia derived from newborn rat brain, observed an ethanol-in duced increase in 2',3'-cyclic nucleotide 3'-phosphohydrolase (a marker for oligodendroglial differentiation) and no change in glutamine synthetase. Furthermore, some investigators have measured significant reductions in the quantity of brain myelin fractions [8][9][10] while others have reported near-normal to increased myelin protein content in offspring exposed to ethanol during gestation [11][12][13][14], Differences in ethanol exposure peri ods and techniques have been suggested as possible rea sons for these discrepancies [10]. Nonetheless, a large body of anatomical, in vitro, and biochemical evidence does suggest that ethanol exposure during development alters, at least to some extent, the process of myelination in the central nervous system.…”

Ethanol in Clinically Relevant Concentrations Enhances Expression of Oligodendroglial Differentiation but Has No Effect on Astrocytic Differentiation or DNA Synthesis in Primary Cultures

“…In general, myelination has been shown to be either slightly impaired or unimpaired in offspring of ethanol-fed animals [58][59][60][61][62][63]. In a study of C-6 glioma cells, the dexamethasone-induced increase in CNP activity was shown to be inhibited by the presence of ethanol in concentrations at least twice the highest concentration in our study [64].…”

Lectin binding sites in axon-myelin-Schwann cell complex.

“…The positive reaction of the axolemma is related to its complex glycoprotein composition (9), including membrane bound enzymes of glycoprotein nature (4). The axoplasmic smooth reticulum and mitochondria are characterized by a very strong Lectin binding capacity.…”