n mitochondria of brown adipose tissue, it has been studied the oxidation
of various substrates, including NADH and ascorbate + cytochrome c, and determined the
activation of Mg2+
-stimulated ATPase. It was revealed that NAD-dependent substrates
(pyruvate + malate, glutamate) are oxidized with a high level of V4 and low RC. However,
on such substrate as succinate, it was detected a higher V4 rate and a lower RC than the
oxidation of NAD-dependent substrate. As well, high oxidation rates of exogenous NADH
and ascorbate + cytochrome c were detected, not coupled with the ATP synthesis. At
application of GDP, it was found a decrease in the respiration rate of V4 on succinate, on
NAD-dependent substrates as well as on the NADH substrate.
At the same time, liver mitochondria have been studied, that have mildly expressed
uncoupled respiration at oxidation of NADH, ascorbate + cytochrome c and other substrates.
In mitochondria of adipose tissue, it was found a high activity of Mg2+
-stimulated
ATPase, sensitive to oligomycin. It has a higher activity than DNP-stimulated ATPase.
In liver mitochondria, it is detected a significantly lower level of exogenous NADH
oxidation as well as Mg2+
-stimulated ATPase than in mitochondria of brown adipose tissue.
The intensive oxidation of exogenous NADH and ascorbate (+ cytochrome c), as well
as high activity of Mg2+
-stimulated ATPase, detected in mitochondria of brown adipose
tissue are explained by the presence of a special membrane-porous subpopulation of
mitochondria in suspension. This subpopulation, that exists separately from the ATPsynthesizing population of mitochondria, is capable of carrying out intense proton leakage
and tissue thermogenesis.