Calcium ion-induced uptakes and transformations of substrates in liver mitochondria

Harris, E. J.; Berent, Celia

doi:10.1042/bj1150645

Cited by 20 publications

(11 citation statements)

References 24 publications

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“…Since the Ca2+/H+ ratio for energised Ca2+ uptake is well established to be 1:1 [7], it follows that the H+/O ratio for Ca2+ uptake supported by /?-hydroxybutyrate oxidation would also be 6 : I. The K+/O ratios reported in the present experiments with valinomycin are lower than found in previous work [23], but it has been shown that with valinomycin energy is preferentially used to make ATP rather than transport K+ [24], and in anaerobic mitochondria there would be ADP competing with K+ for the energy available. However, when free Ca2+ is available, its uptake takes precedence over ATP synthesis [14] so the Ca2+/0 ratio remains insensitive to the ADP level.…”

Section: Discussioncontrasting

confidence: 56%

Cation Uptake as the Basis for Production of Proton Pulses by Mitochondria at the Anaerobic‐Aerobic Transition

Thomas¹,

Manger

Harris

1969

European Journal of Biochemistry

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1. Calcium movement and proton pulse production by mitochondria have been studied using pH-and K+-sensitive glass electrodes and the Ca++ indicator murexide.2. Anaerobic treatment led to the release of free Ca++ into the medium, the quantity depending on the preparative procedure and the composition of the medium.3. The ejection of protons by anaerobic mitochondria given small additions of oxygen was accompanied by the uptake of approximately equal numbers of calcium ions. Addition of ethylene glycol bis (B-aminoethy1)-N,N'-tetraacetic acid (EGTA) reduced the proton pulses to about 40 Ol0 of their maximum size in KC1 medium, and to 5°/0 in a sucrose medium.4. Mitochondria treated with EGTA and valinomycin gave proton pulses that were accompanied by approximately equal uptakes of K+.5. Mitochondria kept anaerobic for 20 min and then aerated were found to be without respiratory control by ADP unless EGTA was added before aeration.6. It is concluded that the production of proton pulses by untreated mitochondria a t the anaerobic-aerobic transition occurs only under conditions where sufficient free Ca++ has leaked out to allow energy-dependent exchange between external Ca++ and internal protons.It has been shown that proton pulse production by mitochondria a t the anaerobic-aerobic transition occurs with strict H+/O ratios for different substrates [l-31. This has been used as evidence for the 'chemiosmotic' theory of energy coupling which states that proton production is directly involved with the synthesis of ATP in mitochondria by an anisotropic ATPase, the energy for ATP synthesis supposedly being derived from a membrane potential arising from the charge separation of H+ and OHacross the sided ATPase within the membrane. The object of the present work has been to investigate whether proton production by mitochondria a t the anaerobic-aerobic transition can be correlated to a respiration-driven Ca uptake, since it has been well established that the energised uptake of Ca++ gives rise to a stoichiometric release of protons [4-71. If Ca++ uptake is the cause of the proton pulse production described by Mitchell, the appearance of protons in the medium is not indicative of an electrostatic charging of the membrane capacity. Since only one positive charge appears externally in exchange for one of the two positive charges on the Ca++, there must be a generation of one internal anion or OH-for each H+ ejected.Unusuul Abbreviation. Ethylene glycol bisv-aminoethyl)-N,N'-tetraacetic acid, EGTA.The use of a Ca++ indicator, murexide, in conjunction with a dual-wavelength spectrophotometer, as described by Chance and Mela [S], permits sufficiently sensitive measurements of Ca++ levels outside the mitochondria to be made during the anaerobicaerobic transition.The production of protons by anaerobic mitochondria in the presence of EGTA and valinomycin has been described by Mitchell and Moyle, who first interpreted it in terms of membrane conductance phenomena [9]. However, they later [lo] gave evidence showing a K+/H+ exchange re...

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Section: Discussioncontrasting

confidence: 56%

Cation Uptake as the Basis for Production of Proton Pulses by Mitochondria at the Anaerobic‐Aerobic Transition

Thomas¹,

Manger

Harris

1969

European Journal of Biochemistry

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“…This effect contributes to the provision of energy for the uptake process. A cotransport of anions with Ca2+ has been described for liver mitochondria (Harris & Berent, 1969) and, by use of high (10-20mM) concentrations, it has been shown that hydroxybutyrate will accompany Ca2+ in Vol. 168 Table 1.…”

Section: Uptake Of Ca2+mentioning

confidence: 99%

“…The rapid uptake of Ca2+ by mitochondria has attracted much attention, partly because there are so many related effects, which include stimulated respiration, shifts of internal and external pH, shifts of redox state (Chance, 1965;Lehninger, 1970), delocalization of respiratory components (Vinogradov et al, 1972;Azzi et al, 1975) and anion uptakes (Harris & Berent, 1969;Brand et al, 1976). The practical question of physiological interest has been whether, and if so how, mitochondrial Ca2+ uptake supplements the activity of the sarcoplasmic reticulum in muscle, especially in the heart.…”

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confidence: 99%

The uptake and release of calcium by heart mitochondria

Harris

1977

Biochemical Journal

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The kinetics of uptake of Ca2+ by rat heart mitochondria were studied by a spectrophotometric method with Arsenazo III indicator. The exponential rate coefficients measured with or without added phosphate increase with the amount of Ca2+ added up to about 24pM. Evidence is given that the effect is attributable to a combination of formation of chelates at low concentrations to act as C2+ buffers, with co-transport of substrate to provide more respiratory fuel. The inhibitory effect of Mg2+ depends on the Ca2+ concentration, so with a constant [Mg2+] the low concentrations of Ca2+ are most inhibited, and the rate coefficients are still more Ca2+-dependent. Ca2+ uptake is slowed by local anaesthetics such as butacaine and dibucaine, and also by propranolol and palmitoyl-CoA.After an uptake, the release of Ca2+ was investigated. The spontaneous release involves an initially slow and small appearance of free Ca2+ and is followed by an auto-accelerated phase. The release is accompanied by a gradual decrease in internal ATP; it is initiated by palmitoyl-CoA (reversed by carnitine), by lysophosphatidylcholine, by Na+ salts (reversed by oligomycin) and by K+ salts added to a K+-free medium containing valinomycin. The process is probably a response to an increased energy load imposed on the mitochondria by the various conditions, which include the spontaneous action ofphospholipase activated by traces of Ca2+. The problem of how much mitochondrial activity is participating in normal heart Ca2+ turnover is discussed, and experiments showing only 7-14 % exchange of the, mitochondrial Ca2+ occurring in vivo in 10 or 20min are reported.

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“…At the end of 5 min the incubation was stopped and the islets were separated from the incubation buffer by centrifugation for 15 s at 8,000 x g in a Greiner microfuge (type ZF1, Greiner A. G., Lucerne, Switzerland). By this procedure (26,28,35,36), the islets were separated from the buffer by passage through the phthalate mixture and into the urea layer. Insulin release was assayed on an aliquot of the supematant buffer.…”

Section: Introductionmentioning

confidence: 99%

The Roles of Intracellular and Extracellular Ca++ in Glucose-Stimulated Biphasic Insulin Release by Rat Islets

Wollheim¹,

Kikuchi²,

Renold³

et al. 1978

J. Clin. Invest.

126

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A B S T R A C T Verapamil, an agent known rapidly to block calcium uptake into islets of Langerhans, has been used to study the roles of intra-and extracellular calcium in the two phases of glucose-induced insulin release. Rates of calcium uptake and insulin release during the first phase were measured simultaneously over 5 min in rat islets after maintenance in tissue culture for 2 days. Rates of 45Ca++ efflux and insulin release during the first and second phases were also measured simultaneously under perifusion conditions. For this, islets were loaded with 45Ca++ during the entire maintenance period to complete isotopic equilibrium. Under static incubation conditions 5 AuM Verapamil had no effect upon Ca++ uptake or insulin release in the presence of 2.8 mM glucose. By contrast, glucose-stimulated calcium influx was totally abolished without there being any significant effect upon first phase insulin release. Thus first phase insulin release is independent of increased uptake of extracellular calcium. The lack of effect of 5 AM Verapamil blockade on first phase insulin release was confirmed, under perifusion conditions, and was in marked contrast to the observed 55% inhibition of second phase release. 45Ca++ efflux was inhibited during both phases of the insulin release response.The results show that increased calcium uptake in response to glucose is not involved in the mechanism of first phase insulin release but is required for the full development and maintenance ofthe second phase release. It seems possible that intracellular calcium is the major regulatory control for first phase insulin release and that intracellular calcium and increased uptake of extracellular calcium contribute almost equally to the second phase ofglucose-induced release.

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Calcium ion-induced uptakes and transformations of substrates in liver mitochondria

Cited by 20 publications

References 24 publications

Cation Uptake as the Basis for Production of Proton Pulses by Mitochondria at the Anaerobic‐Aerobic Transition

Cation Uptake as the Basis for Production of Proton Pulses by Mitochondria at the Anaerobic‐Aerobic Transition

The uptake and release of calcium by heart mitochondria

The Roles of Intracellular and Extracellular Ca++ in Glucose-Stimulated Biphasic Insulin Release by Rat Islets

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