title: Possible involvement of intracellular Ca2+ in hyposmosis-evoked catecholamine release from adrenal chromaffin cells.
abstract: The influence of hyposmotic conditions on catecholamine release was studied using cultured adrenal chromaffin cells. Incubation of the cells in hyposmotic solution led to the enhancement of catecholamine release in a manner dependent on the reduction of osmolarity. Hyposmosis-evoked catecholamine release was similarly observed in the presence or absence of extracellular Ca2+, and was not significantly affected by organic and inorganic Ca2+ entry blockers. These results indicated that the hyposmosis-evoked release might be associated with a rise in the intracellular Ca2+ concentration. Further studies showed that neither ryanodine nor thapsigargin caused any significant effect on hyposmosis-evoked catecholamine release, whereas pretreatment of chromaffin cells with carbonyl cyanide m-chlorophenyl hydrazone significantly enhanced the hyposmosis-evoked release. Catecholamine release evoked by exposure to hyposmotic medium is therefore thought to be mediated through intracellular Ca2+, which may be mainly sequestered by the mitochondrial pools. Neither caffeine- nor inositol 1,4,5-trisphosphate-sensitive Ca2+ pools seems likely to be involved in hyposmosis-evoked catecholamine release, although the Ca2+ pools that contribute to the elevation of intracellular Ca2+ observed under hyposmotic conditions are not yet completely identified.
authors.affiliation: Department of Pharmacology, Tokushima University School of Medicine, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Morita
authors.forename: S
authors.initials: S
authors.lastname: Hamano
authors.forename: K
authors.initials: K
authors.lastname: Teraoka
authors.forename: K
authors.initials: K
authors.lastname: Ishimura
mesh_terms: D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism*; D007038:Hypotonic Solutions; D007424:Intracellular Fluid / Q000502:physiology*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009994:Osmolar Concentration
chemical_list: D002395:Catecholamines; D007038:Hypotonic Solutions; D002118:Calcium