Abstract
We have recently reported that ethanol and other n-alkanols added to in vitro assays inhibit the activity of the Na + Ca 2+ exchange system in brain synaptic plasma membrane vesicles. The present studies were undertaken to determine whether in vivo chronic ethanol administration leads to alterations in this Na + Ca 2+ antiporter that might be indicative of an adaptive response to alcohol. The Na +-dependent Ca 2+ transport activity in the plasma-membrane fractions obtained was measuredd at various Ca 2+ concentrations. Results of these experiments revealed that a 3-week ethanol regimen brought about a significant increase in the Na +-dependent Ca 2+ transport activity only in the membrane fraction enriched in synaptic junctional complexes. These membranes showed a near doubling in the maximal transport activity of the antiporter in alcohol-treated compared with the control animals. Changes in the kinetic parameters were reversible as the Na + Ca 2+ exchange activity in these membranes from animals maintained on alcohol for 3 weeks and then withdrawn for 1 week was indistringuishable from that of membranes from control animals. Thus it appears that ethanol-treated animals make a reversible adaptation in their neuronal cell membranes to compensate for the acute effects of ethanol on the Na + Ca 2+ antiporter.
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