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Uribe, S; Perez-Vazquez, V; Ramirez, J; Aguilera-Aguirre, L; Gonzalez-Hernandez, JC; Clemente-Guerrero, M; Manzo-Avalos, S; Saavedra-Molina, A (2002)

EFFECT OF CA2+ AND MG2+ ON THE MN-SUPEROXIDE DISMUTASE FROM RAT LIVER AND HEART MITOCHONDRIA

AMINO ACIDS 22(4):405-416
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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 Ca2+ ([Ca2+](f)) and free Mg2+ ([Mg2+](f)) on normoxic and hypoxic mitochondria from either organ were tested. In normoxic mitochondria from either tissue, both [Ca2+](f) and [Mg2+](f) activated the enzyme, although [Mg2+](f) was less efficient as an activator and the effect was lower in heart than in liver mitochondria. When added simultaneously, high [Ca2+](f) and [Mg2+](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 [Ca2+](f) plays a role in regulating Mn-SOD in concert with the activation of aerobic metabolism.