title: Effect of Ca(2+) and Mg(2+) on the Mn-superoxide dismutase from rat liver and heart mitochondria.
abstract: The manganese superoxide dismutase (Mn-SOD) converts superoxide anions to hydrogen peroxide plus oxygen, providing the first line of defense against oxidative stress in mitochondria. Heart mitochondria exhibited higher Mn-SOD activity than liver mitochondria. In mitochondria from both tissues Mn-SOD activity decreased after incubation at low oxygen concentration (hypoxic mitochondria). The effects of free Ca(2+) ([Ca(2+)](f)) and free Mg(2+) ([Mg(2+)](f)) on normoxic and hypoxic mitochondria from either organ were tested. In normoxic mitochondria from either tissue, both [Ca(2+)](f) and [Mg(2+)](f) activated the enzyme, although [Mg(2+)](f) was less efficient as an activator and the effect was lower in heart than in liver mitochondria. When added simultaneously, high [Ca(2+)](f) and [Mg(2+)](f) exhibited additive effects which were more pronounced in heart mitochondria and were observed regardless of whether mitochondria had been incubated under normal or low oxygen. The data suggest that [Ca(2+)](f) plays a role in regulating Mn-SOD in concert with the activation of aerobic metabolism.
authors.affiliation: Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacan 58030, México.
authors.forename: V
authors.initials: V
authors.lastname: Pérez-Vázquez
authors.forename: J
authors.initials: J
authors.lastname: Ramírez
authors.forename: L
authors.initials: L
authors.lastname: Aguilera-Aguirre
authors.forename: J C
authors.initials: JC
authors.lastname: González-Hernández
authors.forename: M
authors.initials: M
authors.lastname: Clemente-Guerrero
authors.forename: S
authors.initials: S
authors.lastname: Manzo-Avalos
authors.forename: S
authors.initials: S
authors.lastname: Uribe
authors.forename: A
authors.initials: A
authors.lastname: Saavedra-Molina
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D066298:In Vitro Techniques; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D008929:Mitochondria, Heart / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D018384:Oxidative Stress; D010101:Oxygen Consumption; D051381:Rats; D017208:Rats, Wistar; D013482:Superoxide Dismutase / Q000378:metabolism*
chemical_list: D013482:Superoxide Dismutase; D008274:Magnesium; D002118:Calcium