scholarly journals Modification by calcium ions of adenine nucleotide translocation in rat liver mitochondria

1972 ◽  
Vol 129 (2) ◽  
pp. 355-365 ◽  
Author(s):  
T. Spencer ◽  
F. L. Bygrave
Keyword(s):  
Rat Liver ◽  
Calcium Ions ◽  
Adenine Nucleotide ◽  
Cell Metabolism ◽  
Liver Mitochondria ◽  
High Energy ◽  
Small Degree ◽  
Metabolic Inhibitors ◽  
Rat Liver Mitochondria ◽  
Stimulation Of

1. Added Ca2+stimulates the translocation of ATP by isolated rat liver mitochondria. 2. The apparent Km for added Ca2+in stimulating the translocation of 200μm-ATP is approx. 160μm (75μm ‘free’ Ca2+). 3. The greatest stimulation of ATP translocation by Ca2+occurs at the lower concentrations of ATP. 4. Sr2+(and to a lesser extent Ba2+) can replace Ca2+whereas Mg2+and Mn2+have only little ability to stimulate ATP translocation. 5. Translocation of dATP is also stimulated by Ca2+whereas that of ADP is stimulated to only a relatively small degree. 6. Studies with metabolic inhibitors and uncouplers provide evidence that stimulation by Ca2+and by uncouplers is additive and that the mechanism of Ca2+stimulation does not seem to involve the high-energy intermediate of oxidative phosphorylation. 7. In the presence of Ca2+, ATP is able to effectively compete with ADP for translocation. 8. Added K+further enhances the ability of Ca2+to stimulate ATP translocation. 9. These findings are discussed in relation to the potential involvement of Ca2+in modifying enzymic reactions involved in the regulation of cell metabolism.

Effects of 5-5'-Diphenyl-2-thiohydantoin (DPTH) and Thyroxine on the Ultrastructure and Chemical Composition of Rat Liver

1971 ◽  
Vol 29 ◽  
pp. 570-571
Author(s):  
E. A. Elfont ◽  
R. B. Tobin ◽  
D. G. Colton ◽  
M. A. Mehlman
Keyword(s):  
Chemical Composition ◽  
Rat Liver ◽  
Future Study ◽  
Mode Of Action ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Effective Inhibitor ◽  
Biochemical Effects ◽  
Glycerophosphate Dehydrogenase ◽  
Stimulation Of

Summary5,-5'-diphenyl-2-thiohydantoin (DPTH) is an effective inhibitor of thyroxine (T4) stimulation of α-glycerophosphate dehydrogenase in rat liver mitochondria. Because this finding indicated a possible tool for future study of the mode of action of thyroxine, the ultrastructural and biochemical effects of DPTH and/or thyroxine on rat liver mere investigated.Rats were fed either standard or DPTH (0.06%) diet for 30 days before T4 (250 ug/kg/day) was injected. Injection of T4 occurred daily for 10 days prior to sacrifice. After removal of the liver and kidneys, part of the tissue was frozen at -50°C for later biocheailcal analyses, while the rest was prefixed in buffered 3.5X glutaraldehyde (390 mOs) and post-fixed in buffered 1Z OsO4 (376 mOs). Tissues were embedded in Araldlte 502 and the sections examined in a Zeiss EM 9S.Hepatocytes from hyperthyroid rats (Fig. 2) demonstrated enlarged and more numerous mitochondria than those of controls (Fig. 1). Glycogen was almost totally absent from the cytoplasm of the T4-treated rats.

scholarly journals The effect of butacaine on adenine nucleotide binding and translocation in rat liver mitochondria

1975 ◽  
Vol 148 (3) ◽  
pp. 527-531 ◽  
Author(s):  
D R Fayle ◽  
G J Barritt ◽  
F L Bygrave
Keyword(s):  
Rat Liver ◽  
Local Anaesthetic ◽  
Binding Sites ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Nucleotide Binding ◽  
Local Anaesthetics ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Inner Membrane

The effect of the local anaesthetic, butacaine, on adenine nucleotide binding and translocation in rat liver mitochondria partially depleted of their adenine nucleotide content was investigated. The range of butacaine concentrations that inhibit adenine nucleotide translocation and the extent of the inhibition are similar to the values obtained for native mitochondria. Butacaine does not alter either the total number of atractyloside-sensitive binding sites of depleted mitochondria, or the affinity of these sites for ADP or ATP under conditions where a partial inhibition of the rate of adenine nucleotide translocation is observed. The data are consistent with an effect of butacaine on the process by which adenine nucleotides are transported across the mitochondrial inner membrane rather than on the binding of adenine nucleotides to sites on the adenine nucleotide carrier. The results are briefly discussed in relation to the use of local anaesthetics in investigations of the mechanism of adenine nucleotide translocation.

scholarly journals Factors affecting the translocation of oxaloacetate and l-malate into rat liver mitochondria

1968 ◽  
Vol 109 (5) ◽  
pp. 921-928 ◽  
Author(s):  
J. M. Haslam ◽  
D. E. Griffiths
Keyword(s):  
Rat Liver ◽  
Adenosine Triphosphatase ◽  
Liver Mitochondria ◽  
Spectrophotometric Assay ◽  
Rat Liver Mitochondria ◽  
Anaerobic Conditions ◽  
Factors Affecting ◽  
Adenosine Triphosphatase Activity ◽  
Energy Dependent ◽  
Stimulation Of

1. The rates of translocation of oxaloacetate and l-malate into rat liver mitochondria were measured by a direct spectrophotometric assay. 2. Penetration obeyed Michaelis–Menten kinetics, and apparent Km values were 40μm for oxaloacetate and 0·13mm for l-malate. 3. Arrhenius plots of the temperature-dependence of rates of penetration gave activation energies of +10kcal./mole for oxaloacetate and +8kcal./mole for l-malate. 4. The translocation of both oxaloacetate and l-malate was competitively inhibited by d-malate, succinate, malonate, meso-tartrate, maleate and citraconate. The Ki values of these inhibitors were similar for the penetration of both oxaloacetate and l-malate. 5. Rates of penetration were stimulated by NNN′N′-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate under aerobic conditions or by ATP under anaerobic conditions. 6. The energy-dependent stimulation of translocation was abolished by uncouplers of oxidative phosphorylation. Oligomycin A, aurovertin, octyl-guanidine and atractyloside prevented the stimulation by ATP, but did not inhibit the stimulation by NNN′N′-tetramethyl-p-phenylenediamine dihydrochloride plus ascorbate. 7. Mitochondria prepared in the presence of ethylene-dioxybis(ethyleneamino)tetra-acetic acid did not exhibit the energy-dependent translocation, but this could be restored by the addition of 50μm-calcium chloride. 8. Valinomycin or gramicidin plus potassium chloride enhanced the energy-dependent translocation of oxaloacetate and l-malate. 9. Addition of oxaloacetate stimulated the adenosine triphosphatase activity of the mitochondria, and the ratio of ‘extra’ oxaloacetate translocation to ‘extra’ adenosine triphosphatase activity was 1·6:1. 10. Possible mechanisms for the energy-dependent entry of oxaloacetate and l-malate into mitochondria are discussed in relation to the above results.

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