Adaptation to salinity by fish: Alterations in energy transducing status of muscle mitochondria.

The functional status of fish muscle mitochondria during exposure of the organism to salinity stress was studied. No alterations were observed in the substrate oxidation capacity. However, the mitochondria appear to be in an uncoupled state during the first few days of exposure and recover thereafter. This could be correlated to high endogenous Ca2+ levels in the mitochondria in the early period. A Na+ – Ca2+ antiport in these mitochondria is shown. Evidence is also presented to show that the mitochondria isolated during the early stages of stress are in a swollen state and are unable to contract on addition of ATP and Mg2+ Continued exposure to the stress, however, reverses the situation.