Stimulation of the respiration rate of rat liver mitochondria by sub-micromolar concentrations of extramitochondrial Ca2+.
1. The respiration rate of rat liver mitochondria was stimulated by up to 70% when the extramitochondrial Ca2+ concentration was raised from 103 to 820 nM. This occurred when pyruvate, 2-oxoglutarate, or threo-(Ds)-isocitrate was employed as substrate, but not when succinate was used. 2. Ruthenium Red prevented the stimulation of mitochondrial respiration by extramitochondrial Ca2+, showing that the effect required Ca2+ uptake into the mitochondrial matrix. 3. Starvation of rats for 48 h abolished the stimulation of mitochondrial respiration by extramitochondrial Ca2+ when pyruvate was used as substrate, but did not affect the stimulation of 2-oxoglutarate oxidation by extramitochondrial Ca2+. 4. Our findings are in accord with proposals that oxidative metabolism in liver mitochondria may be stimulated by Ca2+ activation of intramitochondrial dehydrogenases.
Johnston
J D
JD
Department of Biochemistry, University of Cambridge, U.K.
Brand
M D
MD
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D005260:Female; D007523:Isocitrates / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D010101:Oxygen Consumption / Q000187:drug effects*; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation / Q000378:metabolism; D013268:Stimulation, Chemical; D013386:Succinates / Q000378:metabolism; D019802:Succinic Acid
D007523:Isocitrates; D007656:Ketoglutaric Acids; D011773:Pyruvates; D013386:Succinates; D019289:Pyruvic Acid; C034219:isocitric acid; D019802:Succinic Acid; D002118:Calcium