Arachidonic acid-induced dye uncoupling in rat cortical astrocytes is mediated by arachidonic acid byproducts
Keywords: acid, oxygen, inhibition, rat, localization, enzyme, transport, junction, animals, phosphorylation, serum, brain, rats, protein, cell, calcium, synthase, dyes, embryo, species, astrocytes, astrocyte, melatonin, bovine, radical, albumin, radicals, cortex, article, gap, lipoxygenase, dye, concentration, controlled, prostaglandin, fluorescent, animal, study, isoquinolines, response, derivative, priority, nonhuman, journal, Cells,, Cultured, Free, Reactive, Cerebral, arachidonic, Albumin,, Prostaglandin-Endoperoxide, Synthases
Arachidonic acid (AA) induced a concentration- and time-dependent reduction in gap junction-mediated dye coupling between cultured astrocytes. The effect was greatly diminished by inhibition of cyclooxygenases and lipoxygenases. The action of a low concentration of AA (5 ?M) was also prevented by Ca2+-free extracellular solution or a high concentration of melatonin, a potent free radical scavenger, but not by N?-nitro-L-arginine, a nitric oxide (NO) synthase inhibitor. Thus, this effect may depend on Ca2+ influx and oxygen free radicals but not on NO generation. Cellular uncoupling induced by a high (100 ?M), but not a low, AA concentration was rapidly reversed by washing with albumin containing solution. After reversal from 5 min but not 2.5 min inhibition with a high AA concentration dye coupling between astrocytes became refractory to a low concentration of AA, suggesting desensitization of the response elicited by a low concentration of the fatty acid. Dye uncoupling occurred without changes in levels and state of phosphorylation (immunoblotting and 32P-incorporation) of connexin43, the main astrocyte gap junctional protein. However, maximal cell uncoupling induced by a low (Slow action) but not by a high (Fast action) AA concentration was paralleled by a reduction in connexin43 (immunofluorescence) at cell-to-cell contacts. It is proposed that the AA- induced dye uncoupling is mediated by byproducts that induce rapid channel closure or slow removal of connexin43 gap junctions.
|Título de la Revista:||Brain research|
|Fecha de publicación:||1999|
|Página de inicio:||411|