PubMed Health⌕ Search

Biomedical subjects

D Siliprandi

Publications and source records attributed to D Siliprandi.

At least 37 records · Page 2Linked to original sources
PubMed1983

On the relationship between calcium and phosphate transport, transmembrane potential and acetoacetate-induced oxidation of pyridine nucleotides in rat-liver mitochondria.

Acetoacetate addition to rat liver mitochondria induces a complete oxidation of pyridine nucleotides, a collapse of membrane potential, a release of mitochondrial Ca2+ and a loss of respiratory control only in the presence of external phosphate. Acetoacetate also enhances the efflux of mitochondrial Mg2+ promoted by phosphate. All these effects are not only prevented but also reversed, except the oxidation of pyridine nucleotides, by the combined addition of Mg2+, ADP and dithioerythritol to damaged mitochondria. It is concluded that acetoacetate, through the oxidation of mitochondrial pyridine nucleotides, potentiates the action of phosphate in altering the mitochondrial permeability barrier, which is closely dependent on the maintenance of membrane thiol groups in a reduced form.

Acetoacetates↗
PubMed1981

Parallel efflux of Ca2+ and Pi in energized rat liver mitochondria.

Addition of Ruthenium Red to energized rat liver mitochondria that have previously accumulated Ca2+ and phosphate from the external medium induces a parallel efflux of both these ions. Mersalyl or dithioerythritol, which decrease Ruthenium Red-insensitive Ca2+ efflux, also decrease phosphate efflux to the same extent. Conversely diazenedicarboxylic acid bis(NN-dimethylamide) (DDBA), which increases the Ruthenium Red-induced Ca2+ efflux concurrently increases phosphate release. Dithioerythritol and DDBA, reducing and oxidizing agents of thiol groups respectively, modify Ca2+ and Pi efflux without penetrating the mitochondrial inner membrane. Under all the adopted conditions the membrane potential is preserved. The release of resting respiration and the parallel efflux of Mg2+ and adenine nucleotides, events closely correlated to Ca2+ cycling, are equally prevented either by mersalyl, which inhibits phosphate transport, or dithioerythritol; DDBA has the opposite effect. These findings and the observation that suggest that Ca2+ and phosphate transport in energized liver mitochondria are closely related and dependent on the redox state of membrane-bound thiol groups.

Adenine Nucleotides↗
PubMed1981

Correlated effluxes of adenine nucleotides, Mg2+ and Ca2+ induced in rat-liver mitochondria by external Ca2+ and phosphate.

The presence of inorganic phosphate and Ca2+ in the external medium induces a closely parallel efflux of both endogenous adenine nucleotides and Mg2+ from rat liver mitochondria. These effluxes are (a) pH-dependent and inhibited by uncouplers, respiration inhibitors and external Mg2+; (b) completely prevented by bongkrekate, but stimulated by atractylate. ATP, ADP or AMP each inhibit the release of Mg2+ promoted by Ca2+ and phosphate; however, in the presence of oligomycin and P1,P5-di(adenosine-5')-pentaphosphate (an inhibitor of adenylate kinase) only ADP is effective. Also the release of accumulated Ca2+ observed when approximately 50% Mg2+ is discharged is retarded by bongkrekate and added Mg2+ whereas it is accelerated by atractylate. All adenine nucleotides have a significant effect in retarding the efflux of accumulated Ca2+ but, in the presence of oligomycin and P1,P5-di(adenosine-5')-pentaphosphate, only ADP is active. From these results we conclude that effluxes of Mg2+, Ca2+ and adenine nucleotide from rat liver mitochondria induced by external phosphate are interconnected and regulated by external ADP and Mg2+ levels.

Adenine Nucleotides↗
PubMed1978

Efflux of magnesium and potassium ions from liver mitochondria induced by inorganic phosphate and by diamide.

Addition to rat liver mitochondria of 2 mM inorganic phosphate or 0.15 mM diamide, a thiol-oxidizing agent, induced an efflux of endogenous Mg2+ linear with time and dependent on coupled respiration. No net Ca2+ release occurred under these conditions, while a concomitant release of K+ was observed. Mg2+ efflux mediated either by Pi or low concentration of diamide was completely prevented by EGTA, Ruthenium red, and NEM. These reagents also inhibited the increased rate of state 4 respiration induced both by Pi and diamide. At higher concentrations (0.4 mM), diamide induced an efflux of Mg2+ which was associated also with a release of endogenous Ca2+. Under these conditions EGTA completely prevented Mg2+ and K+ effluxes, while they were only partially inhibited by Ruthenium red and NEM. It is assumed that Mg2+ efflux, occurring at low diamide concentrations or in the presence of phosphate, is dependent on a cyclic in-and-out movement of Ca2+ across the inner mitochondrial membrane, in which the passive efflux is compensated by a continuous energy linked reuptake. This explains the dependence of Mg2+ efflux on coupled respiration, as well as the increased rate of state 4 respiration. The dependence of Mg2+ efflux on phosphate transport is explained by the phosphate requirement for Ca2+ movement.

Animals↗