Effects of Manganese (Mn) Supplementation on Muscle Force Generation during Hypoxia.


1Benson, M., 1Receno, C.,2Mohamed, Z., 2DeRuisseau, L., 1DeRuisseau, K. 1Syracuse University, Syracuse, NY, 2 Le Moyne College, Syracuse, NY

Purpose: Impaired skeletal muscle contractile function and increased oxidative stress were previously shown to occur during exposure to hypoxic conditions. Notably, antioxidants were shown to attenuate the hypoxia-mediated declines in skeletal muscle function. In the mitochondria, manganese (Mn) plays a role in the normal functioning of manganese superoxide dismutase (MnSOD); a key antioxidant enzyme. Manganese administration could lead to increased MnSOD activity and thus attenuate the skeletal muscle dysfunction that is observed during hypoxia. Methods: Eleven week old male CD-1 mice were assigned to receive either saline (S; n=8) or manganese chloride (Mn; n=8) i.p. injections (12mg/kg body mass) once per day for 7 days. Animals were anesthetized with isoflurane and the diaphragm was quickly harvested. Diaphragm strips were dissected and vertically suspended in a Kreb’s- Henseleit buffer maintained at 37°C. Skeletal muscle twitch and tetanic force generation (N/cm2) measurements were obtained under normoxia conditions (95%O2; 5%CO2). Force frequency (20Hz, 30Hz, 60Hz, 150Hz, 200Hz) and baseline force measurements were obtained following a 30 minute incubation in hypoxia (95%N2; 5%CO2) conditions. Animal body mass and muscle contractile characteristics were analyzed using an independent samples t-test. Force frequency data were analyzed using a 2-way repeated measures ANOVA using SPSS Statistics 20 and significance was set at pResults: No differences in animal mass (p>0.05), normoxia peak twitch tension (S: 2.4±0.21 vs. Mn: 2.2±0.38; p>0.05), or normoxia peak tetanic tension (S: 15.6±0.81 vs. Mn: 15.8±1.32; p>0.05) were observed. The rise in baseline force following 30 minutes of hypoxia was not significant when expressed in absolute values (C: 0.34±.08 vs. Mn: 0.47±.09; p>0.05) or as a percentage of maximal force generation (C: 2.35±0.64 vs. Mn: 2.80±0.39; p>0.05). No differences were observed in muscle force generation at any of the frequencies examined when normalized (N/cm2) or expressed as a percentage of maximal force generation (p>0.05). Conclusion: Short term manganese supplementation did not alter skeletal muscle contractile function during exposure to hypoxia.

Research funded by Le Moyne College Biological Sciences Department

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