title: ATP-stimulated accumulation of calcium by chromaffin granules and mitochondria from the adrenal medulla.
abstract: In the presence of high concentrations of free Ca2+ (10(-5) - 10(-4) M) chromaffin granules and adrenal medullary mitochondria take up large amounts of Ca2+. At low levels of buffered free Ca2+ (less than 10(-8) M), these mitochondria release almost all of their stored calcium, whereas chromaffin granules retain the major part of their calcium pool. In the presence of MgATP and at less than 10(-8) M free Ca2+, the mitochondria do not take up significant amounts of Ca2+. Chromaffin granules, however, under the same conditions, show active MgATP-dependent Ca2+ uptake even at nM-concentrations of free Ca2+. The implications of these results for the calcium metabolism of chromaffin cells are discussed.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D002837:Chromaffin Granules / Q000378:metabolism*; D002838:Chromaffin System / Q000378:metabolism*; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism*
chemical_list: D000255:Adenosine Triphosphate; D002118:Calcium