Effect of Ca(2+) and Mg(2+) on the Mn-superoxide dismutase from rat liver and heart mitochondria.
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.
Pérez-Vázquez
V
V
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacan 58030, México.
Ramírez
J
J
Aguilera-Aguirre
L
L
González-Hernández
J C
JC
Clemente-Guerrero
M
M
Manzo-Avalos
S
S
Uribe
S
S
Saavedra-Molina
A
A
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*
D013482:Superoxide Dismutase; D008274:Magnesium; D002118:Calcium