Premium
Rat extraocular muscles use lactate as mitochondrial substrate
Author(s) -
Snider Natalie Nicole,
GarciaCazarin Mary Lolis,
Andrade Francisco Humberto
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1051.24
Subject(s) - respiration , malate dehydrogenase , mitochondrion , lactate dehydrogenase , biology , glutamate receptor , biochemistry , oligomycin , citrate synthase , nad+ kinase , cellular respiration , substrate (aquarium) , enzyme , anatomy , ecology , atpase , receptor
Extraocular muscles (EOMs) have unique adaptations to match the demands imposed by constant activity. We previously showed that lactate is a potential energy source in EOMs, not metabolic waste. Here, we tested the hypothesis that EOM mitochondria can use lactate. We isolated mitochondria from EOMs of adult male Sprague Dawley rats to measure respiration (O2 consumption) by polarography. State 2 respiration started with glutamate/malate, lactate/malate or lactate/malate plus NAD+. ADP initiated state 3 respiration. Oligomycin, an ATP synthase inhibitor, was used to estimate state 4. Uncoupled respiration, state 5, was determined by adding carbonyl cyanide‐p‐trifluoromethoxyphenylhydrazone. A respiratory control ratio (state 3/state 4) ≥ 4 was evidence of viable mitochondria. We determined lactate dehydrogenase (LDH) content by western blot. There was no significant difference in O2 consumption with lactate/malate or lactate/malate plus NAD+ when compared to glutamate/malate for states 2, 4, and 5 (p≥ 0.05). However, state 3 was higher with glutamate/malate compared to lactate/malate (p=0.004). There were no differences in state 3 with other substrates. LDH is present in EOM mitochondria. We conclude that rat EOMs can use lactate as a metabolic substrate for mitochondrial respiration and that mitochondrial LDH is likely responsible for oxidation of lactate to pyruvate. Supported by R01 EY012998 to FHA.