Exchange of potassium ions across a concentration difference by isolated rat-liver mitochondria

Amoore, John E.

doi:10.1042/bj0760438

Cited by 22 publications

(8 citation statements)

References 14 publications

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“…12) must represent the consequence of turnover of a labile fraction. In common with Amoore (1960) we find that though some 40% of the K+ is exchanged within 1 min. this proportion does not then increase over 20min.…”

Section: Resultssupporting

confidence: 69%

“…this proportion does not then increase over 20min. Amoore (1960) did obtain further exchange in 40min. and still more in 60min., but at these times there had been appreciable losses of K+.…”

Section: Resultsmentioning

confidence: 99%

“…The net gain of K+ by particles suspended in media either capable of supporting oxidative phosphorylation or containing ATP has been demonstrated (Share, 1958;Gamble, 1962;Christie, Ahmed, McLean & Judah, 1965;Rottenberg & Solomon, 1965). That the uptake is not due to occlusion or formation of an undissociated compound is inferred from measurements of tracer 42K+ uptake though, indeed, a part of the K+ exchanges slowly (Gamble, 1957;Amoore, 1960).…”

mentioning

confidence: 99%

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Induced and spontaneous movements of potassium ions into mitochondria

Harris¹,

Cockrell²,

Pressman³

1966

Biochemical Journal

108

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1. Net movements of K(+) into metabolizing liver mitochondria before and after the addition of valinomycin have been measured by using selective glass electrodes. The advantage of using an automatic titrator to hold the K(+) concentration constant is demonstrated. 2. According to the energy source provided the induced movement after the addition of valinomycin can be either in or out. 3. Uptakes and rates of movement are higher in media containing acetate (20mm) than in media containing chloride (20mm). In each mixture comparisons were made at three pH values; at pH6.36 the induced rates are less than at pH7.0 or 7.8 but the final uptakes attained are increased. 4. The rate of uptake is increased by inorganic phosphate. 5. The presence of Mg(2+) slightly decreases the induced uptake and rate of movement; Ca(2+) can cause the induced movement of K(+) to be outward. 6. The rate of induced K(+) movement is related to the rate of extra oxygen consumption but with different factors in acetate (24 K(+) ions/oxygen molecule) and chloride media (10 K(+) ions/oxygen molecule). 7. The amount of K(+) gained is proportional to the loss of fluorescence of the suspension. 8. When K(+) moves there is a contrary movement of H(+) but the ratio depends on the conditions. At pH6.36 in chloride media the K(+)/H(+) ratio exceeded 10:1 and in no case did it fall to unity. 9. When K(+) is taken up there is a proportional diminution of light-scattering; it is inferred that swelling takes place along with K(+) accumulation. 10. It is shown by the use of tracer (42)K(+) that turnover of the ion in mitochondria is increased by valinomycin. 11. It is concluded that valinomycin both increases the permeability to K(+) and also, given an adequate energy supply, stimulates the K(+)-accumulating mechanism.

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Section: Resultssupporting

confidence: 69%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Induced and spontaneous movements of potassium ions into mitochondria

Harris¹,

Cockrell²,

Pressman³

1966

Biochemical Journal

108

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“…Lack of penetration of respiration-inhibited or uncoupled mitochondria by alkali-metal cations The results just described are difficult to reconcile with the generally accepted view that K+ hardly penetrates the mitochondrial membrane at all in the absence of ionophorous antibiotics (see, e.g., Gamble, 1957; Amoore & Bartley, 1958;Amoore, 1960;Rottenberg & Solomon, 1965;Christie et al, 1965;Harris et al, 1967) or enters in sluggish antiport for H+ (Mitchell & Moyle, 1967, 1969. Repetition of the swelling experiments described by Chappell & Crofts (1966) as a criterion of mitochondrial permeability revealed that respiration-inhibited blowfly flightmuscle mitochondria do not swell in iso-osmotic potassium chloride, potassium acetate or tetramethylammonium acetate solutions, whereas they swell with great rapidity in iso-osmotic ammonium acetate or phosphate solutions, supporting the idea that the K+ ion is indeed a non-penetrant when mitochondria are not respiring.…”

Section: Conditionmentioning

confidence: 87%

“…For some time there has been general consensus that the inner mitochondrial membrane is essentially impermeable to alkali-metal cations. This view, originally suggested by the observation that a portion of the mitochondrial K+ is retained during sucrose washing (Spector, 1953;Bartley & Davis, 1954;Amoore, 1960) and by the osmotic behaviour of mitochondria in solutions of potassium salts (Chappell, 1954;Tedeschi, 1961), was strengthened by the demonstration of a low rate of exchange of endogenous K+ with added 42K (Gamble, 1957;Amoore & Bartley, 1958). Such exchange experiments removed the ambiguity of earlier work in which gross fluxes of K+ were involved, in that the latter are always associated with the movement of at least one other ion, which may be the limiting factor.…”

mentioning

confidence: 99%

The effect of the coupled oxidation of substrate on the permeability of blowfly flight-muscle mitochondria to potassium and other cations

Hansford

Lehninger

1972

Biochemical Journal

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1. Blowfly flight-muscle mitochondria respiring in the absence of phosphate acceptor (i.e. in state 4) take up greater amounts of K(+), Na(+), choline, phosphate and Cl(-) (but less NH(4) (+)) than non-respiring control mitochondria. 2. Uptake of cations is accompanied by an increase in the volume of the mitochondrial matrix, determined with the use of [(14)C]-sucrose and (3)H(2)O. The osmolarity of the salt solution taken up was approximately that of the suspending medium. 3. The [(14)C]sucrose-inaccessible space decreased with increasing osmolarity of potassium chloride in the suspending medium, confirming that the blowfly mitochondrion behaves as an osmometer. 4. Light-scattering studies showed that both respiratory substrate and a permeant anion such as phosphate or acetate are required for rapid and massive entry of K(+), which occurs in an electrophoretic process rather than in exchange for H(+). The increase in permeability to K(+) and other cations is probably the result of a large increase in the exposed area of inner membrane surface in these mitochondria, with no intrinsic increase in the permeability per unit area. 5. No increase in permeability to K(+) and other cations occurs during phosphorylation of ADP in state 3 respiration.

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