The effect of calcium on the respiratory responses of mung bean mitochondria.
Purified mung bean hypocotyl mitochondria were examined for their capacity to carry out respiration-dependent accumulation of calcium. The addition of 0.1-1.0 mM calcium to mung bean mitochondria supplemented with succinate gave no stimulation of state 4 respiration even in the presence of inorganic phosphate and the ionophoretic antibiotic A-23187. Even at high calcium concentrations, no transient changes in the respiratory activity occurred and subsequent addition of ADP initiated a further state 3 response. Although the additions of calcium resulted in a rapid H+ ejection, it was insensitive to lanthanum and uncoupling agents. Similarly, additions of calcium failed to initiate any transient changes in the oxidation-reduction states of either pyridine nucleotides or cytochrome b. Direct spectrophotometric recordings of absorbance changes of murexide revealed no respiration-linked calcium transport. It is proposed that although mung bean mitochondria possess a respiration-linked electrochemical potential gradient it would appear that this potential cannot be expressed as calcium transport even at high ion concentrations, probably due to a low calcium membrane permeability.
D000693:Anaerobiosis; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D003580:Cytochromes / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009550:Nigericin / Q000494:pharmacology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects*; D010944:Plants / Q000378:metabolism*; D013053:Spectrophotometry; D014634:Valinomycin / Q000494:pharmacology
D003580:Cytochromes; D014634:Valinomycin; D000001:Calcimycin; D004492:Edetic Acid; D009550:Nigericin; D002118:Calcium