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A Rendon

Publications and source records attributed to A Rendon.

At least 55 records · Page 3Linked to original sources
PubMed1985

Compartmentation of enzymes: ATP citrate lyase in hepatocytes from fed or fasted rats.

Compared with traditional techniques of tissue homogenization, digitonin fractionation of isolated hepatocytes provides a much more rapid and, in some instances, more accurate determination of enzyme compartmentation. Results with ATP citrate lyase (EC 4.1.3.8) illustrate the information that uniquely can be obtained. Although the enzyme was previously thought to be entirely cytosolic, digitonin fractionation has shown that a portion of total cellular ATP citrate lyase is bound to mitochondria or some other structure, and the amount bound varies with the animal's nutritional state. In hepatocytes from rats that were starved for 2 days, fed NIH stock diet ab libitum, or starved for 2 days and then refed a fat-free diet for 2 days, the noncytosolic activity was, respectively, 52, 21, or 24% of total cellular lyase. However, because starvation/refeeding greatly induces lipogenic enzymes, the amount of bound lyase activity in this dietary state was 10-12 times greater than that in rats that were starved or fed ad libitum. The association of citrate lyase with a subcellular organelle is also influenced by CoA. Addition of 20 microM CoA to the digitonin fractionation medium caused all of the lyase to be released from cells like a cytosolic enzyme. Conversely, when cellular free CoA was decreased by incubating hepatocytes with the hypolipidemic agent 5-(tetradecyloxy)-2-furoic acid, the amount of bound lyase was increased. These results suggest the possibility that the noncytosolic ATP citrate lyase may have a special role in lipogenesis.

ATP Citrate (pro-S)-Lyase↗
PubMed1983

Interaction of antimycin with cytochrome b-561. A study in secretory granules and in plasma membrane isolated from chromaffin cells of bovine adrenal medulla.

Cytochrome b-561 in chromaffin granules interacts with antimycin and its alpha-peak shifts 1 nm towards red. When chromaffin granules were treated with Triton X-100 antimycin no effect was observed. Cytochrome b-561 is located in the plasma membrane isolated from the chromaffin cells. The plasma membrane b-561 does not seem to interact with antimycin. A number of NADH or NADPH (acceptor) oxidoreductase activity has been observed in isolated plasma membrane providing clues to the origin of plasma membrane dehydrogenase. The possible role of cytochrome b-561 in secretory granules other than its accredited energy conserving electron transport property is projected.

Adrenal Medulla↗
PubMed1980

Translocation of mitochondrial aspartate aminotransferase through mitochondrial inner membrane. A cross-linking study with dimethyladipimidate.

Mitoplasts isolated from rat liver mitochondria were treated with dimethyladipimidate, a bifunctional alkylating agent. This agent causes, concurrently with modification of amino groups, loss of osmotic response. It was found that after cross-linking, the movement effector, succinate, was unable to induce the aspartate aminotransferase release from mitoplasts. In contrast, dimethyladipimidate-treated mitoplasts were still able to internalize 125I-labeled aspartate aminotransferase upon removal of exogenous succinate. The possible involvement of membrane asymmetry in the mechanism of translocation of porteins through the inner mitochondrial membrane is discussed.

Animals↗
PubMed1979

Direct evidence for internalization of mitochondrial aspartate aminotransferase into mitoplasts.

Mitochondrial aspartate aminotransferase, an enzyme localized on the inner face of the inner mitochondrial membrane, is released into the intermembrane space upon addition of a "movement effector" (succinate, fumarate, pyruvate, or glutamate) [Waksman, A., & Rendon, A. (1974) Biochimie 56, 907-924]. After removal of the movement effector, 90% of the released enzyme rebound to mitoplasts. Lubrol fractionation showed that this bound activity was associated with the inner membrane. Internalization was demonstrated by using both enzymatic and molecular approaches. It was found that 70% of the reassociated enzyme became inaccessible from the outside of the mitoplast either to a nonpermeating substrate (NADH), to mild protease hydrolysis, or to recognition by a specific antibody. In contrast, in inside-out vesicles, the enzyme remained accessible to NADH, protease, and antibodies. Latency measurements performed at different temperatures on whole intact mitochondria confirmed the existence of reversible intermembrane movement of the enzyme in situ.

Animals↗
PubMed1977

Intramitochondrial intermembranal reversible translocation of aspartate aminotransferase and malate dehydrogenase through the inner mitochondrial membrane.

The translocation of aspartate aminotransferase, malate dehydrogenase, and bulk protein from the rat liver inner mitochondrial membrane and matrix toward the intermembranal space induced by certain organic acids (movement effectors) has been studied. Experiments involving a two-stage dissolution of the mitochondrial membranes by the use of detergents strongly suggest that enzymes like aspartate amino-transferase can cross the inner mitochondrial membrane providing exogenous movement effector was present. Experiments which measured the changes in membranal distribution of malate dehydrogenase induced by the movement effectors also suggested the occurrence of a similar phenomenon for this enzyme in intact mitochondria. Control experiments revealed that under our experimental conditions, the inner mitochondrial membrane remained impermeable to small molecules, e.g., sucrose, and that the release of aspartate aminotransferease, malate dehydrogenase, insocitrate dehydrogenase, and bulk protein into the intermembranal space in the presence of succinate occurred at a much lower concentration of digitonin than that required to disrupt the inner mitochondrial membrane.

Animals↗
PubMed1977

[Reversible enlargement of proteins in rat liver mitochondria: analysis by polyacrylamide gel electrophoresis].

Intramitochondrial large amplitude protein movements were studied by polyacrylamide gel electrophoresis on the intermembranal fluids of mitochondria which were incubated in presence of movement effectors. The specific and reversible property of this phenomenon was confirmed by this method. Its bilateral nature was observed. The eventuality of a partial inner membrane damage provoked by the synergic action of digitonine and movement effector, was discussed, evaluated and dismissed.

Animals↗
PubMedDate not supplied

Inhibition of oxidative phosphorylation in hepatic and cerebral mitochondria of sodium valproate-treated rats.

Rats were treated with intraperitoneal injections of sodium valproate (VPA), either acutely, one injection VPA 200 mg/kg, or chronically, VPA 600 mg/kg/day for 5 days, and the oxygen consumption, MO2, of isolated hepatic and cerebral mitochondria measured. For hepatic mitochondria, Stade IV MO2 decreased by more than 20%, and Stage III MO2 by more than 50%, in the presence of succinate or glutamate-malate substrates. A decoupling agent intensified this inhibition. With cerebral mitochondria, the effects were similar but weaker, for pyruvate-malate or glutamate-malate substrates. These findings suggest that VPA, a short-chain fatty acid, may affect the properties of the internal mitochondrial membrane, although an action on substrate carriers, or on indispensable mitochondrial metabolites, is not excluded. Inhibition of oxidative phosphorylation cannot, however, alone account for hepatotoxicities seen in VPA-treated subjects. These are rare, whereas inhibition of mitochondrial respiration by VPA is consistently observed.

Adenosine Diphosphate↗