scholarly journals Stimulation of hepatic sodium and potassium-activated adenosine triphosphatase activity by phenobarbital. Its possible role in regulation of bile flow.

1977 ◽  
Vol 59 (5) ◽  
pp. 849-861 ◽  
Author(s):  
F R Simon ◽  
E Sutherland ◽  
L Accatino
Keyword(s):  
Bile Flow ◽  
Adenosine Triphosphatase ◽  
Adenosine Triphosphatase Activity ◽  
Sodium And Potassium ◽  
Stimulation Of

scholarly journals Environmental CO2 Stimulation of Mitochondrial Adenosine Triphosphatase Activity

1963 ◽  
Vol 238 (2) ◽  
pp. 836-842
Author(s):  
D.D. Fanestil ◽  
A Baird Hastings ◽  
Theodore A. Mahowald
Keyword(s):  
Adenosine Triphosphatase ◽  
Adenosine Triphosphatase Activity ◽  
Stimulation Of

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.

scholarly journals Temperature-dependence of activation and inhibition of rat-brain adenosine triphosphatase activated by sodium and potassium ions

1966 ◽  
Vol 100 (3) ◽  
pp. 762-767 ◽  
Author(s):  
N Gruener ◽  
Y Avi-Dor
Keyword(s):  
Rat Brain ◽  
Adenosine Triphosphatase ◽  
Arrhenius Plot ◽  
Enzyme System ◽  
The Other ◽  
Potassium Ions ◽  
Adenosine Triphosphatase Activity ◽  
Brain Microsomes ◽  
High Concentrations ◽  
Sodium And Potassium

1. The adenosine-triphosphatase activity of rat-brain microsomes was measured between 0 degrees and 37 degrees . The stimulatory effect of Na(+) plus K(+) on the Mg(2+)-dependent adenosine-triphosphatase activity decreased sharply with decreasing temperature and became negligible at 0 degrees . An Arrhenius plot drawn from the experimental data showed two discontinuities: one at about 6 degrees and the other at about 20 degrees . 2. The increment in activity induced by Na(+) plus K(+) was more sensitive to oligomycin at lower than at higher temperatures, but the opposite was observed for ouabain. The action of oligomycin showed a biphasic character, since below a certain concentration it caused slight activation of Na(+)-plus-K(+)-activated adenosine triphosphatase. 3. Where oligomycin increased the activity of the enzyme, it also enhanced the accumulation of an acid-precipitable phosphorylated compound formed through the transfer of the gamma-phosphate group of [(32)P]ATP to the enzyme system. Stimulatory concentrations of oligomycin did not interfere with K(+)-mediated dephosphorylation of the intermediate, though high concentrations of oligomycin counteracted the effect of K(+). 4. The temperature profile of K(+)-stimulated microsomal phosphatase qualitatively resembled that of microsomal adenosine triphosphatase.

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