Modification by calcium ions of adenine nucleotide translocation in rat liver mitochondria.
1. Added Ca(2+) stimulates the translocation of ATP by isolated rat liver mitochondria. 2. The apparent K(m) for added Ca(2+) in stimulating the translocation of 200mum-ATP is approx. 160mum (75mum ;free' Ca(2+)). 3. The greatest stimulation of ATP translocation by Ca(2+) occurs at the lower concentrations of ATP. 4. Sr(2+) (and to a lesser extent Ba(2+)) can replace Ca(2+) whereas Mg(2+) and Mn(2+) have only little ability to stimulate ATP translocation. 5. Translocation of dATP is also stimulated by Ca(2+) whereas that of ADP is stimulated to only a relatively small degree. 6. Studies with metabolic inhibitors and uncouplers provide evidence that stimulation by Ca(2+) and by uncouplers is additive and that the mechanism of Ca(2+) stimulation does not seem to involve the high-energy intermediate of oxidative phosphorylation. 7. In the presence of Ca(2+), ATP is able to effectively compete with ADP for translocation. 8. Added K(+) further enhances the ability of Ca(2+) to stimulate ATP translocation. 9. These findings are discussed in relation to the potential involvement of Ca(2+) in modifying enzymic reactions involved in the regulation of cell metabolism.
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D001464:Barium / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002869:Chromosome Aberrations / Q000187:drug effects*; D066298:In Vitro Techniques; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D009840:Oligomycins / Q000494:pharmacology; D010085:Oxidative Phosphorylation; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D013324:Strontium / Q000494:pharmacology; D014449:Tyrothricin / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
D009840:Oligomycins; D014449:Tyrothricin; D014634:Valinomycin; D001464:Barium; D008345:Manganese; D000244:Adenosine Diphosphate; D000968:Antimycin A; D000255:Adenosine Triphosphate; D011188:Potassium; D002118:Calcium; D013324:Strontium