Hydrogen shuttles in gills of water versus air breathing osteoglossids.
1. Using subcellular preparations of gills from Arapaima, an obligate air breather, and aruana, a related osteoglossid that is an obligate water breather, a comparison was made of the relative roles of the malate-aspartate cycle and the alpha-glycerophosphate (alpha-GP) cycle in transferring reducing equivalents from the cytosol to the mitochondria. 2. In aruana gill preparations, the alpha-GP cycle could be most clearly demonstrated by reconstructing it with purified isolated mitochondria, using the oxidation rate of exogenous NADH as a measure of the cycling activity. 3. Subcellular preparations of Arapaima gill, in contrast to the aruana gill, were not responsive to exogenous alpha-glycerophosphate, but a glutamate-malate stimulated O2 uptake was sensitive to aminooxyacetate, an aminotransferase inhibitor, a result that would be expected if the respiration were based on malate-aspartate cycling. 4. It was concluded that, compared to the alpha-glycerophosphate cycle, the malate-aspartate cycle was relatively more active in Arapaima gill than in aruana gill, and possible implications were discussed.
D000388:Air; D000818:Animals; D005399:Fishes / Q000502:physiology*; D005880:Gills / Q000378:metabolism*; D006859:Hydrogen; D008929:Mitochondria, Heart / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D012119:Respiration; D014867:Water
D014867:Water; D006859:Hydrogen