Ethanol actions on the mechanisms of Ca2+ mobilization in rat hippocampal cells are mediated by protein kinase C.
The effects of ethanol on intracellular free Ca(2+) concentration, [Ca](i), were studied in cultured rat hippocampal neurons using fluo-3 and confocal microscopy. Ethanol application transiently elevAted [Ca](i) due to Ca(2+)-induced Ca(2+) release from internal stores since the effect was observed also in solutions containing zero Ca(2+) or 0.3 mM La(3+) and restoration of external Ca(2+) content led to secondary response in presence of ethanol. The sites of highest [Ca]i increases correlated well with those obtained after Ca(2+) release from caffeine-and IP3-sensitive internal stores. After single ethanol exposure the caffeine-evoked [Ca](i) transients were potentiated whereas Ca(2+) release induced by IP(3)-mobilizing agonists was suppressed. Similar effects were observed by activation of protein kinase C (PKC) by phorbol esters which also occluded ethanol actions. Ethanol increased fluorescence of Rim-1, a PKC indicator dye. The data obtained are consistent with ethanol activation of PKC whereby Ca(2+) release via ryanodine receptors is potentiated and IP(3) receptors are down-modulated. Since the effects of both ethanol and phorbol esters were mimicked by cytochalasins B and D, PKC-induced cytoskeleton phosphorylation and its subsequent rearrangements can be responsible for observed effects.
Mironov
S L
SL
University of Salzburg, Department of Animal Physiology, Institute for Zoology, Salzburg, Austria.
Hermann
A
A
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology*; D006624:Hippocampus / Q000187:drug effects*; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D010703:Phorbol Esters; D000431:Ethanol; D011493:Protein Kinase C; D002118:Calcium