Manganese is essential for normal development and activity of the nervous tissue. Mn2+ ions are involved in protein synthesis and may prevent free radical damage. Since it is now established that alcohol degradation may produce free radicals, we studied the effect of Mn2+ on ethanol induced alterations using cultured nerve cells as an experimental model of the central nervous system. Neurons and glial cells were cultured from rat brain cortex; a tumoral rat glial cell line (C6) was also examined. We measured enzymatic markers of nerve cell maturation (enolase, glutamine synthetase) and superoxide dismutase, a scavenger of free radicals; all these enzymes being activated by Mn2+ ions. Only for the glial cell types an alcohol antagonizing effect was found when Mn2+ was combined with ethanol. Neurons were not sensitive to that Mn2+ effect.
Nuclear poly(ADP-ribose) polymerase levels as well as the DNA strand break levels of whole-brain neuronal and astroglial cells were investigated . Three-and 30month-old rats were used . Low-molecular-weight neurofilaments and glutamine synthetase served as neuronal and astroglial markers, respectively . A large increase in the poly(ADP-ribose] polymerase activity was observed in the neurons (threefold) and astrocytes (3 .7-fold) derived from 30-month-old rats . Similarly, the amount of poly(ADP-ribose) polymerase, evaluated per milligram of DNA, in-creased~3 .5-fold in neurons and 3 .9-fold in astrocytes prepared from 30-month-old rats . Whether the increase in the poly(ADP-ribose) polymerase activity was due to an enhanced rate of DNA strand break was investigated by determining the rate of DNA unwinding . A significant increase in DNA unwinding rate was detected in the neurons {2 .7-fold}, although a lower increase was observed in the astroglia (1 .3-fold) of aged animals .
The effect of alcohol on enzymes involved in energy metabolism of nervous tissue were analyzed, in vivo after acute and chronic ethanol administration to rats and in vitro by addition of 50 mM and 100 mM ethanol to the medium of cultured nerve cells: chick neurons, chick glial cells, a neuronal cell line (MT17) and a glial tumoral cell line (C6). The parameters we measured were (Na+, K+), Mg2+ and ecto Ca2+, Mg2+ ATPase activities involved in transport phenomena and enolase activities (non neuronal NNE and neuron specific enolase NSE) as markers of nerve cell maturation. In vivo, after chronic ethanol administration (Na+, K+) ATPase activity was increased while Mg2+ dependent activity was not affected. Enolase activity was decreased. Acute ethanol administration decreased (Na+, K+) ATPase activity, while Mg2+ dependent activity was not affected. In cultured nerve cells ethanol effect was dose, time and cell type dependent; alterations of the cell membrane by trypsinization of the tissue before seeding modifies the effect of ethanol on the enzymes we analyzed. Our results suggest that alcohol effect on nerve cells depends mainly on the lipoprotein structure of the cell membranes which may have different properties from one cell type to another.
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