scholarly journals Effects of calmodulin antagonists on the active Ca2+ uptake by rat liver mitochondria

1983 ◽  
Vol 214 (3) ◽  
pp. 929-935 ◽  
Author(s):  
M G P Vale ◽  
A J M Moreno ◽  
A P Carvalho
Keyword(s):  
Rat Liver ◽  
Atp Hydrolysis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Atpase ◽  
Calmodulin Antagonists ◽  
Carrier System ◽  
Specific Substance ◽  
Phenothiazine Drugs ◽  
Mitochondrial Atpase Activity

The mechanism of Ca2+ transport by rat liver mitochondria was investigated with respect to the possible involvement of calmodulin in this process. We studied the action of exogenous calmodulin isolated from brain tissue on the Ca2+-transport system, as well as the effect of two types of calmodulin antagonists; the phenothiazine drugs trifluoperazine and chlorpromazine and the more specific substance compound 48/80. Our results show that Ca2+ transport by mitochondria and mitochondrial ATPase activity are insensitive to exogenous calmodulin, although they can be inhibited by the phenothiazines. Since no effect of compound 48/80 was observed, we believe that the phenothiazines act through a mechanism that does not involve calmodulin. This is in accord with our inability to locate significant quantities of calmodulin in mitochondria by radioimmunoassay analysis. Our results further show that trifluoperazine and chlorpromazine also inhibit the electron-carrier system of the respiratory chain, and this effect may mediate their inhibitory action on Ca2+ transport when it is energized by respiration instead of ATP hydrolysis.

scholarly journals Studies on the nature of the high-affinity trialkyltin binding site of rat liver mitochondria

1982 ◽  
Vol 202 (1) ◽  
pp. 163-169 ◽  
Author(s):  
A P Dawson ◽  
B G Farrow ◽  
M J Selwyn
Keyword(s):  
Binding Site ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Affinity Binding ◽  
Mitochondrial Atpase ◽  
High Affinity Binding ◽  
High Affinity ◽  
High Affinity Binding Site ◽  
Triphenyltin Chloride

1. The proteolipid fraction isolated from rat liver mitochondria pretreated with [3H]triphenyltin chloride is enriched in triphenyltin compared with the original mitochondria. 2. Part of this [3H]triphenyltin is eluted with a protein of Mr 5000-6000 on Sephadex LH20 chromatography. 2. Mössbauer spectra of the proteolipid fraction treated with 119Sn-enriched triethyltin chloride show a doublet which corresponds closely with that assigned previously [Farrow & Dawson (1978) Eur. J. Biochem. 86. 85-95] to the absorption of triethyltin bound to the high-affinity binding site of the mitochondrial ATPase.

scholarly journals The synthesis of hippurate from benzoate and glycine by rat liver mitochondria. Submitochondrial localization and kinetics

1977 ◽  
Vol 166 (1) ◽  
pp. 39-47 ◽  
Author(s):  
S J Gatley ◽  
H S A Sherratt
Keyword(s):  
Rat Liver ◽  
Atp Hydrolysis ◽  
Atp Synthesis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
O2 Consumption ◽  
Mitochondrial Content ◽  
Presence And Absence ◽  
The Individual ◽  
Good Agreement

1. Rat liver mitochondria make hippurate at up to 4 nmol/min per mg of protein. The rate of synthesis supported by oxidation of glutamate with exogenous Pi present is identical with that supported by ATP plus oligomycin. Lower rates were obtained with other respiratory substrates, and when glutamate was used without Pi. 2. A matrix localization for hippurate synthesis is indicated by the latency of benzoyl-CoA synthetase and glycine N-acyltransferase to their extramitochondrial substrates, failure of exogenous benzoyl-CoA to inhibit incorporation of [14C]hippurate and inhibition of hippurate synthesis supported by ATP, but not glutamate, by carboxyatractyloside. 3. The relative activities of the individual enzymes and the mitochondrial content of benzoyl-CoA in the presence and absence of glycine suggest that hippurate synthesis is rate-limited by formation of benzoyl-CoA. 4. The increases in rates of ATP hydrolysis and of O2 consumption on the addition of benzoate and glycine were in good agreement with those required to support hippurate synthesis. The increase in respiration indicates that State-4 respiration [Chance & Williams (1957) Adv. Enzymol 17, 65-134] is not used, with these conditions, for ATP synthesis.

scholarly journals Characterization of phosphate efflux pathways in rat liver mitochondria

1983 ◽  
Vol 212 (2) ◽  
pp. 279-288 ◽  
Author(s):  
R S Kaplan ◽  
P L Pedersen
Keyword(s):  
Rat Liver ◽  
Transport System ◽  
Atp Hydrolysis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Current View ◽  
Mitochondrial Inner Membrane ◽  
Efflux Pathway ◽  
Hydrolysis Of

ATP hydrolysis catalysed by the H+-ATPase of intact mitochondria can be induced by addition of ATP in the presence of valinomycin and KCl. This leads to an increase in intramitochondrial Pi and therefore allows investigation of potential Pi efflux pathways in intact mitochondria. Combining this approach with the direct measurement of both internal and external Pi, we have attempted to determine whether Pi efflux occurs via an atractyloside-sensitive transporter, by the classical operation of the Pi/H+ and Pi/dicarboxylate carriers, and/or by other mechanisms. Initial experiments re-examined the evidence that led to the current view that one efflux pathway for Pi is an atractyloside-sensitive ATP/ADP,0.5Pi transporter. No evidence was found in support of this efflux pathway. Rather, atractyloside-sensitivity of the low rate of Pi efflux observed in previous studies (oligomycin present) was accounted for by ATP entry on the well known ATP/ADP transport system followed by hydrolysis of ATP and subsequent Pi efflux. Thus, under these conditions, where ATP hydrolysis is not completely inhibited, Pi efflux becomes atractyloside sensitive most likely because this inhibitor blocks ATP entry, not because it directly inhibits Pi efflux. Substantial efflux of Pi from rat liver mitochondria is observed on generation of high levels of matrix Pi by ATP hydrolysis induced by valinomycin and K+ (oligomycin absent). A portion of this efflux can be inhibited by thiol-specific reagents at concentrations that normally inhibit the Pi/H+ and Pi/dicarboxylate carriers. However, a significant fraction of efflux continues even in the presence of p-chloromercuribenzoate, N-ethylmaleimide plus n-butylmalonate or mersalyl. The mersalyl-insensitive Pi efflux, which is also insensitive to carboxyatractyloside, is a saturable process, thus suggesting carrier mediation. During this efflux the mitochondrial inner membrane retains considerable impermeability to other low-molecular-weight anions (i.e., malate, 2-oxoglutarate). In conclusion, results presented here rule out an atractyloside-sensitive ATP/ADP,0.5Pi transport system as a mechanism for Pi efflux in rat liver mitochondria. Rather Pi efflux appears to occur on the classical Pi/H+ transport system as well as via a mersalyl-insensitive saturable process. The inhibitor-insensitive Pi efflux may occur on a portion of the Pi/H+ carrier molecules that exist in a state different from that normally catalysing Pi influx. Alternatively, a separate Pi efflux carrier may exist.

The Enthalpy Change of the Hydrolysis of Adenosine Triphosphate by Rat Liver Mitochondria

1971 ◽  
Vol 49 (6) ◽  
pp. 721-729 ◽  
Author(s):  
Roberto Cereijo-Santaló
Keyword(s):  
Rat Liver ◽  
Atp Hydrolysis ◽  
Liver Mitochondria ◽  
Enthalpy Change ◽  
Rat Liver Mitochondria ◽  
Kcal Mole ◽  
Time Limits ◽  
Differential Calorimeter ◽  
Hydrolysis Of ◽  
Enthalpy Of Ionization

The enthalpy change of the hydrolysis of ATP by rat liver mitochondria was studied using a differential calorimeter. This calorimeter is capable of working as a perfect adiabatic system within the time limits and temperature gradients of our experiments. Samples can be withdrawn from the incubation medium without interference with the temperature measurements.The enthalpy of ionization of Tris was found to be −11.28 ± 0.17 kcal mole−1. The enthalpy of ATP hydrolysis in the presence of either 2,4-dinitrophenol or valinomycin was −6.2 ± 0.1 kcal mole−1.

scholarly journals Citreoviridin, a specific inhibitor of the mitochondiral adenosine triphosphatase

1978 ◽  
Vol 170 (3) ◽  
pp. 503-510 ◽  
Author(s):  
P E Linnett ◽  
A D Mitchell ◽  
M D Osselton ◽  
L J Mulheirn ◽  
R B Beechey
Keyword(s):  
Rat Liver ◽  
Adenosine Triphosphatase ◽  
Specific Inhibitor ◽  
Liver Mitochondria ◽  
Mass Action ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Atpase ◽  
Submitochondrial Particles ◽  
Inhibitory Potency ◽  
Dissociation Constant Kd

1. Citreoviridin was a potent inhibitor of the soluble mitochondrial ATPase (adenosine triphosphatase) similar to the closely related aurovertins B and D. 2. Citreoviridin inhibited the following mitochondrial energy-linked reactions also: ADP-stimulated respiration in whole mitochondria from ox heart and rat liver; ATP-driven reduction of NAD+ by succinate; ATP-driven NAD transhydrogenase and ATPase from ox heart submitochondrial particles. 3. The dissociation constant (KD) calculated by a simple law-of-mass-action treatment for the citreoviridin–ATPase complex was 0.5–4.2micron for ox-heart mitochondrial preparations and 0.15micron for rat liver mitochondria. 4. Monoacetylation of citreoviridin decreased its inhibitory potency (KD=2–25micron, ox heart; KD=0.7micron, rat liver). Diacetylation greatly decreased the inhibitory potency (KD=60–215micron, ox heart). 5. Hydrogenation of citreoviridin monoacetate diminished its inhibitory potency considerably. 6. No significant enhancement of fluorescence was observed when citreoviridin interacted with the mitochondrial ATPase.

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