title: Net adenine nucleotide transport in rat liver mitochondria is affected by both the matrix and the external ATP/ADP ratios.
abstract: The adenine nucleotide pool size of rat liver mitochondria may be regulated by a transport mechanism which allows net movement of ATP or ADP across the inner mitochondrial membrane (J. R. Aprille and J. Austin (1981) Arch. Biochem. Biophys. 212, 689-699). Since transport can occur in either direction, and ATP is the preferred substrate, variations in the matrix or external ATP/ADP ratio were examined for an effect on the direction and rate of net adenine nucleotide flux. Fastest rates of net uptake were seen when the external ATP/ADP ratio was high and the internal ratio was low. Conversely, if the external ratio was low and the internal ratio was high, net loss was observed. The rate and direction of net transport were also changed by simply varying the external ATP concentration alone between 0 and 4 mM. Concentrations of less than 1 mM produced net loss of matrix adenines, whereas higher concentrations caused a net increase. The results suggest that changes in relative concentrations of ATP in the external and internal compartments can result in changes in the adenine nucleotide pool size. Another important result was clarification of earlier ambiguous findings with carboxyatractyloside. If care was taken to avoid changes in the matrix ATP/ADP ratio, the addition of carboxyatractyloside had no effect on either net uptake or net efflux of adenine nucleotides.
mesh_terms: D000227:Adenine Nucleotides / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D000227:Adenine Nucleotides; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate