Structural transformations during swelling of polycomplex matrices based on countercharged (meth)acrylate copolymers (Eudragit EPO/Eudragit L 100-55).

With a view to the application in oral controlled drug delivery systems (DDS), the design of new interpolyelectrolyte complexes (IPECs) between countercharged types of Eudragit EPO (EPO) and Eudragit L 100-55 (L100-55) was investigated. The formation and composition of four new IPECs between EPO and L100-55 were established by elementary analysis. The structure of the synthesized IPEC was investigated using FTIR spectroscopy and modulated-temperature differential scanning calorimetry.

Short-term hypothermia activates hepatic mitochondrial sn-glycerol-3-phosphate dehydrogenase and thermogenic systems.

The contribution of the sn-glycerol-3-phosphate (G-3-P) shuttle in the control of energy metabolism is well established. It is also known that its activity may be modulated by hormones involved in thermogenesis, such as thyroid hormones or dehydroepiandrosterone and its metabolites, that act by inducing de novo synthesis of mitochondrial G-3-P dehydrogenase (mGPDH). However, little is known as to the factors that may influence the activity without enzyme induction.

Opposite role of changes in mitochondrial membrane potential in different apoptotic processes.

We have studied the role of changes in mitochondrial membrane potential (DeltaPsi) in two widely-used models of apoptosis, such as dexamethasone-treated rat thymocytes and U937 human cells treated with tumor necrosis factor-alpha and cycloheximide. To dissipate DeltaPsi, we used low concentrations of valinomycin, unable per se to induce apoptosis, and demonstrated that the decline in DeltaPsi exerts opposite effects in the two models. Indeed, in U937 cells, depolarization of mitochondria increased apoptosis, which decreased in rat thymocytes.

Decrease in mitochondrial energy coupling by thyroid hormones: a physiological effect rather than a pathological hyperthyroidism consequence.

The effect of the in vivo thyroid status on mitochondrial membrane potential (delta psi(m)) in isolated rat hepatocytes was studies by means of a cytofluorimetric technique and the delta psi(m)-specific probe JC-1. It is shown that the delta psi(m) level decreases in the order hypothyroid > euthyroid > hyperthyroid. Polarographic measurement of the hepatocyte respiratory rates revealed an opposite trend of values: the highest respiratory rate in hepatocytes from hyperthyroid animals, the lowest in those from hypothyroid ones.

Use of flow cytometry as a tool to study mitochondrial membrane potential in isolated, living hepatocytes.

The present paper describes the possibility of determination of mitochondrial membrane potential (Deltapsi) in isolated hepatocytes making use of a Deltapsi-sensitive dye, i.e., the lipophilic cationic probe 5,5',6,6'-tetrachloro-1,1',3, 3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1) and of cytofluorimetry.

The effects of the ergosteroid 7-oxo-dehydroepiandrosterone on mitochondrial membrane potential: possible relationship to thermogenesis.

Administered 3 beta-hydroxyandrost-5-ene-7,17-dione (7-oxo-DHEA) is more effective than 3 beta-hydroxyandrost-5-en-7-one (DHEA) as an inducer of liver mitochondrial sn-glycerol-3-phosphate dehydrogenase and cytosolic malic enzyme in rats. Like DHEA, the 7-oxo metabolite enhances liver catalase, fatty acylCoA oxidase, cytosolic sn-glycerol-3-phosphate dehydrogenase, mitochondrial substrate oxidation rate, and the reconstructed sn-glycerol 3-phosphate shuttle. The mitochondrial adenine nucleotide carrier is diminished by thyroidectomy and is restored to normal activity by administering 7-oxo-DHEA.

Effect of cardiolipin on functional properties of isolated rat liver mitochondria.

The specific involvement of cardiolipin in modulating and/or controlling the activity of a number of mitochondrial carriers, enzymes and receptors is well documented; however, comparatively less understood is its role for the integrated functions of intact mitochondria. The aim of the present research was to get a better insight into this problem by investigating the effect of in vitro addition of cardiolipin on the properties of isolated liver mitochondria. The results obtained show that cardiolipin induces extensive structural and functional perturbations at the level of the inner mitochondrial membrane.

Effects of dehydroepiandrosterone and carnitine treatment on rat liver.

It is well established that DHEA treatment is associated in the rat to an increase in fatty acids metabolism. This condition would require levels of L-carnitine much higher than those physiologically present in the liver. The possibility thus exist that during DHEA treatment the concentration of L-carnitine may become a limiting factor for fatty acids oxidation and therefore responsible of some of the effects observed after administration of the hormone.

[Uncoupling action of fatty acids in liver cells].

Oleate (10-60 microM) stimulates oxygen consumption in hepatocytes in the presence of oligomycin. This stimulation of respiration is partially suppressed by 20 microM carboxyatractylate but is insensitive to 0.5 microM cyclosporin A.

Fatty acid-induced Ca(2+)-dependent uncoupling and activation of external pathway of NADH oxidation are coupled to cyclosporin A-sensitive mitochondrial permeability transition.

Permeabilization of inner mitochondrial membrane by palmitic acid in the presence of Ca2+ (cyclosporin A-sensitive stimulation of respiration, decrease of delta psi and high amplitude swelling) is accompanied by activation of the external pathway of NADH oxidation in liver mitochondria. The "pore"-sealing agents (cyclosporin A, Mg2+ with ADP, and L-carnitine with ATP) are equally effective in preventing the induction of external pathway of NADH oxidation by Ca2+ with palmitate. However, activities of these agents are different in respect to recoupling of permeabilized mitochondria.

[Oxidative phosphorylation uncoupling by fatty acids in liver and muscle mitochondria].

Pathways and mechanisms of oxidative phosphorylation uncoupling by long-chain fatty acids in liver and muscle mitochondria are considered. A conclusion is drawn that there exist at least three different pathways of uncoupling by fatty acids, namely: (i) a Ca(2+)-dependent cyclosporin A-sensitive pathway; (ii) uncoupling which is inhibited by carboxyatractylate or other inhibitors of the ADP/ATP-antiporter, (iii) uncoupling due to the low protonophoric activity of fatty acids.

[The protective effect of cyclosporine A, carnitine, and Mg(2+) with ADP during calcium(2+)-dependent permeabilization of mitochondria by fatty acids and activation of NADH oxidation by an external pathway].

The ability of cyclosporin A, Mg2+ plus ADP and L-carnitine to enhance energy recoupling in liver mitochondria and to inhibit the induction of the external pathway of NADH oxidation during Ca(2+)-dependent oxidative phosphorylation uncoupling by palmitate has been studied. Cyclosporin A, Mg2+ plus ADP and L-carnitine plus ATP prevent with an equal efficiency the induction of the external pathway of NADH oxidation by palmitate and Ca2+ in mitochondria but differ drastically by their ability to increase the coupling in permeabilized mitochondria. The recoupling effect of cyclosporin is manifested after addition of Mg2+ plus ADP.

Comparative studies of effects of dehydroepiandrosterone on rat and chicken liver.

1. An attempt to identify the cause of decrease of gain in body weight during dehydroepiandrosterone (DHEA) treatment was made comparing the effects of hormone treatment on chickens and rats. 2.

Concerning the mechanism of increased thermogenesis in rats treated with dehydroepiandrosterone.

Dehydroepiandrosterone (DHEA) treatment of rats decreases gain of body weight without affecting food intake; simultaneously, the activities of liver malic enzyme and cytosolic glycerol-3-P dehydrogenase are increased. In the present study experiments were conducted to test the possibility that DHEA enhances thermogenesis and decreases metabolic efficiency via transhydrogenation of cytosolic NADPH into mitochondrial FADH2 with a consequent loss of energy as heat. The following results provide evidence which supports the proposed hypothesis: (a) the activities of cytosolic enzymes involved in NADPH production (malic enzyme, cytosolic isocitrate dehydrogenase, and aconitase) are increased after DHEA treatment; (b) cytosolic glycerol-3-P dehydrogenase may use both NAD+ and NADP+ as coenzymes; (c) activities of both cytosolic and mitochondrial forms of glycerol-3-P dehydrogenase are increased by DHEA treatment; (d) cytosol obtained from DHEA-treated rats synthesizes more glycerol-3-P during incubation with fructose-1,6-P2 (used as source of dihydroxyacetone phosphate) and NADP+; the addition of citrate in vitro further increases this difference; (e) mitochondria prepared from DHEA-treated rats more rapidly consume glycerol-3-P added exogenously or formed endogenously in the cytosol in the presence of fructose-1,6-P2 and NADP+.

[Damage to calcium ion-loaded mitochondria by fatty acids and the protective effect of carnitine].

The effect of fatty acids and L-carnitine on Ca2+ retention in rat liver mitochondria have been studied. Ca(2+)-retention was estimated as a sum of consecutive Ca2+ additions which leaded to transient stimulation of respiration coupled with influx of Ca2+ L-carnitine increases the Ca(2+)-retention; such an effect requires ATP. The Ca(2+)-retention was increased in the presence of 50 microM ATP or ADP.

Interaction of carnitine with mitochondrial cardiolipin.

The physiological role of L-carnitine is to determine the transport of acyl-CoA through the mitochondrial membrane. However, some observations may also suggest a direct effect of the molecule per se on the physical properties of the membrane, most probably at the level of the binding site. This possibility has been investigated by studying the influence of adriamycin, a drug that binds to cardiolipin, on the effect of carnitine on isolated rat liver mitochondria.

Changes in liver structure and function after short-term and long-term treatment of rats with dehydroepiandrosterone.

The effects on the liver of feeding a diet containing 0.2% dehydroepiandrosterone were studied after short (7 d) and long (100 d) periods of treatment in rats. The short-term treatment caused hypertrophy of the hepatocytes that, at the ultrastructural level, seemed to be due to proliferation of peroxisomes and (to a minor extent) of mitochondria.

Uncoupling effect of fatty acids on heart muscle mitochondria and submitochondrial particles.

The effect of ATP/ADP-antiporter inhibitors on palmitate-induced uncoupling was studied in heart muscle mitochondria and inside-out submitochondrial particles. In both systems palmitate is found to decrease the respiration-generated membrane potential. In mitochondria, this effect is specifically abolished by carboxyatractylate (CAtr) a non-penetrating inhibitor of antiporter.

The protecting effect of L-carnitine on Ca(2+)-loaded rat liver mitochondria.

It is shown that L-carnitine strongly increases the ability of rat liver mitochondria to respond to the train of Ca2+ additions by a transient stimulation of the State-4 respiration rate. Such an effect requires ATP and the L-carnitine efficiency strongly decreases when ATP is omitted. Oleate influences the mitochondria in a fashion opposite to that of L-carnitine.