[Effect of GDP and carboxyatractylate on potassium ion transport in brown fat mitochondria].

It has been shown that the increase of the membrane potential in uncoupled brown fat mitochondria after addition of 1-2 mM GDP to a medium containing potassium acetate is accompanied by swelling of mitochondria which occurs in two phases. The first swelling phase is due to the electrogenic transport of K+ ions, while the second one is activated by carboxyatractylate and carnitine. The swelling is practically completely inhibited by a further rise of the GDP concentration irrespective of high values of the membrane potential. Unlike K+ transport, the potential-dependent transport of Na+ ions occurs more rapidly, is monophasic and insensitive to carboxyatractylate and carnitine. It is suggested that regulation of K+ ion transport in brown fat mitochondria is mediated by the action of nucleotides and fatty acid esters on the uncoupling protein and ADP/ATP antiporter.