title: Phenotypic plasticity of cultured bovine chromaffin cells. II. Fiber outgrowth induced by elevated potassium: morphology and ionic requirements.
abstract: Chromaffin cells isolated from the adult bovine adrenal medulla extend neurite-like processes in culture in response to a variety of agents. In the present study we investigated the effect of chronic depolarization by high potassium on fiber outgrowth and its ionic requirements. Elevated K+ in the culture medium induced process formation of isolated bovine chromaffin cells in a dose-dependent fashion, and so did veratridine. Short-term depolarization by acetylcholine or carbachol caused increased flattening out of the cells, but no outgrowth of neurite-like processes. Formation of processes was accompanied by a significant reduction of endogenous catecholamines in cultured cells after 18 h and 8 days and a relative shift towards storage of primary amines after 8 days. K+-induced fiber outgrowth was dependent on the presence of Ca2+ in the medium and Ca2+-influx into the cells: the effect was inhibited by EDTA, EGTA, CoCl2 and verapamil and mimicked by the Ca2+ ionophore A 23187. Tetrodotoxin, tetraethylammonium, amiloride and ouabain, which interfere with Na+- and K+-fluxes, did not inhibit K+-induced process formation nor did any of them by itself evoke fiber outgrowth. Fiber outgrowth required de novo protein synthesis as shown by the inhibitory effect of cycloheximide. K+-induced formation of processes was not affected by dexamethasone and dbcAMP, both of which inhibit NGF-induced neurite formation of early postnatal rat chromaffin cells in vitro. These results document that chronic depolarization may induce de novo formation of neurite-like processes of bovine chromaffin cells in vitro by a Ca2+- and protein synthesis-dependent mechanism.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002417:Cattle; D002838:Chromaffin System / Q000166:cytology* / Q000648:ultrastructure; D000242:Cyclic AMP / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000096:biosynthesis; D009473:Neuronal Plasticity / Q000187:drug effects*; D010641:Phenotype; D011188:Potassium / Q000494:pharmacology*; D012964:Sodium / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
chemical_list: D009419:Nerve Tissue Proteins; D014701:Veratridine; D003907:Dexamethasone; D012964:Sodium; D000242:Cyclic AMP; D011188:Potassium; D002118:Calcium