Natural distribution and occurrence of coenzyme Q homologues

The knowledge of coenzyme Q levels in tissues, organs, and subcellular compartments is of outstanding interest. A wide amount of data regarding coenzyme Q distribution and occurrence was collected in the last decades; nevertheless the data are often hard to compare because of the different extraction methods and different analytical techniques used. We have undertaken a systematic study for detecting the ubiquinone content in subcellular compartments, cells, and whole-tissue homogenates by a previously standardized HPLC method performed after an extraction procedure identical for all samples. It was confirmed that the major coenzyme Q homologue in rat tissues is coenzyme Q9; however, it was pointed out that all the rodents samples tested contain more than one coenzyme Q homologue. The coenzyme Q homologue distribution is tissue dependent with relatively high coenzyme Q10 content in brain mitochondria, irrespective of the rat strain used. There is no constant relationship of the coenzyme Q content in mitochondria and microsomes fractions. Most organisms tested (including other mammals, bird and fish specimens) have only coenzyme Q10, while the protozoan Tetrahymena pyriformis contains only coenzyme Q8.

Antihypertensive activity of indolepyruvic acid: a keto analogue of tryptophan

We studied the effect of indole-3-pyruvic acid (IPA) on systolic blood pressure of normotensive, spontaneously hypertensive, DOCA + salt hypertensive, and Grollman hypertensive rats. Experiments were also carried out in order to investigate whether IPA may influence the development of hypertension in spontaneously hypertensive rats. Age-matched normotensive, spontaneously hypertensive, DOCA + salt hypertensive, and Grollman hypertensive rats treated with N-methylglucamine, were used as controls. Acute oral (up to 50 mg/kg) and intravenous (5 mg/kg) administration of IPA did not change systolic blood pressure in any models of hypertension. By contrast, a repeated administration of IPA (100 mg/kg/day, by oral gavage for 10 days) significantly decreased systolic blood pressure in all models of hypertension, while it elicited no significant effect in normotensive rats. Moreover, when IPA was given daily to 5-week-old spontaneously hypertensive rats for 7 weeks, it partially inhibited the development of hypertension. In addition, chronic administration of IPA caused enhanced levels of tryptophan and 5-hydroxyindoleacetic acid in the cortex and diencephalon. Brainstem serotonin content in both normotensive and spontaneously hypertensive rats was also enhanced by IPA treatment. Our results suggest that IPA lowers blood pressure in different rat models of hypertension and this effect seems to be correlated with an increase in cerebral serotonin metabolism.

Enzyme activities in perikaryal and synaptic mitochondrial fractions from rat hippocampus during development

When pharmacological or basic neurochemical systematic characterization of mitochondrial enzymatic systems correlated to energy transduction processes is attempted, studies must be based on subcellular fractions with a high degree of purity from specific brain areas and from individual animals. Distinct populations of mitochondria heterogenous with respect to biochemical enzyme characteristics from rat brain hippocampus are described. Two mitochondrial populations were derived from synaptosomes by lysis and a third consists of free non-synaptic mitochondria. The maximum rate of some cerebral enzyme activities which are part of energy transduction (citrate synthase, malate dehydrogenase; total NADH-cytochrome c reductase, cytochrome oxidase) and amino acid metabolism (glutamate dehydrogenase) were tested on these mitochondrial populations of 8- and 16-week-old rats. A comprehensive analysis of the data suggests that extensive but highly diversified catalytic expressions of the enzymes studied occur in the hippocampus. This is true even when a short period of the rat life span is studied. Hence the varying pattern of evolution of the differing cerebral mitochondria, probably a consequence of different metabolic functions, should be taken into account in any pharmacological study on these systems.

A critique on the preparation and enzymatic characterization of synaptic and nonsynaptic mitochondria from hippocampus

1. In literature two interesting methods are described to obtain from whole pooled brains or areas three types of mitochondria, namely, those of perikaryal origin and those contained in synaptosomes. 2. However, for many types of studies, such "preparative" preparations are not useful; for example, in pharmacological studies only data from a single n number of animals may be of statistical usefulness and may be correctly analyzed by statistical tests. 3. Thus a method is described by which it was possible to characterize by enzyme activities three populations from single rat brain hippocampus. 4. During preparative "analytical" procedure, it was noted that the 10% Ficoll gradients previously used in the literature were unable to separate purified mitochondria-free mitochondria. This gradient should be 12% Ficoll for single areas. 5. In addition, when results are compared using the more appropriate omega 2t for calculations of gravity forces to be applied instead of the maximum or average g for different rotors, enzymatic characterization differed considerably among the various mitochondrial populations. 6. The above considerations are also true when different pestle clearances and/or pestle rotations speeds are used during omogenizations; also lysis conditions are essential. 7. Results showed that selected experimental conditions are to be used when subcellular fractions are to be analyzed biochemically.

Superoxide dismutase and cytochrome oxidase activities in light and heavy synaptic mitochondria from rat cerebral cortex during aging

The specific activities of superoxide dismutase (SOD) and cytochrome oxidase (COX) in light and heavy synaptic mitochondria from rat cerebral cortex at different ages (4, 8, 12, 16, 20, and 24 months) have been measured. The specific activity of COX was significantly higher in light synaptic mitochondria than in heavy ones at all ages examined. However, no significant difference during aging was shown. A marked decrease of SOD in light and heavy synaptic mitochondria during aging was observed.

Action of piracetam and clonidine on different mitochondrial populations from hippocampus

The maximum rate (Vmax) of some mitochondrial enzymatic activities related to energy transduction (citrate synthase, malate dehydrogenase, NADH-cytochrome c reductase (as total activity), cytochrome oxidase) and amino acid metabolism (glutamate dehydrogenase) were evaluated in non-synaptic (free) and synaptic mitochondria from rat brain hippocampus. Three types of mitochondria were isolated from rats subjected to single i.p. treatments with piracetam (300 mg.kg-1) or with clonidine (750 micrograms.kg-1). With respect to the enzymatic pattern of three types of non-synaptic and synaptic mitochondria, in hippocampus a different maximum rate of both NADH-cytochrome c reductase and cytochrome oxidase was observed, these activities in particular being lowest in the "synaptic heavy" mitochondrial subfraction than in the "synaptic light" one; in addition, other enzyme activities are different in the "free" as compared to both the "light" and "heavy" mitochondria. This confirms that in various types of brain mitochondria a different metabolic machinery exists. Acute treatment with piracetam decreased citrate synthase, glutamate dehydrogenase, NADH-cytochrome c reductase and cytochrome oxidase activities only in the "heavy" mitochondria obtained from synaptosomes. Acute treatment with clonidine decreased the citrate synthase, NADH-cytochrome c reductase and cytochrome oxidase activities only in the same type of mitochondria, i.e. synaptic "heavy" mitochondria. However, this drug increased the same enzymatic activities in "free" mitochondria, some of them being increased or decreased in "light" intrasynaptic ones. Therefore in vivo administration of piracetam mainly affects some specific enzyme activities (suggesting a specific molecular trigger mode of action) of the intrasynaptic mitochondria (suggesting a specific subcellular trigger site of action), the effect on enzyme activities by clonidine being more complex.

Influence of some ergot alkaloids on the cerebral reduced glutathione

Dose-related changes of the reduced glutathione were evaluated in forebrains from male Wistar rats aged 10 months after chronic i.p. treatment for two months with the ergot alkaloids dihydroergocristine and dihydroergocriptine. The results indicate that, within a specific dose-range, the concentration of the cerebral reduced glutathione may be modified by exogenous intervention.

Energetic state of aged brain during hypoxia

Synaptosomes isolated from the forebrain of rats of different ages (20, 60, 100 and 140 weeks of age) and incubated in Krebs-Henseleit-Hepes pH 7.4 buffer (for 10 min at 24 degrees C) were utilized to define the redox state of the intramitochondrial NAD couple (delta Gox-red) and the phosphorylation state of adenine nucleotide system (delta GATP). The free-energy change (delta delta G) for the coupled reactions was calculated. The animals were subjected for 10 min to different degrees of in vivo hypoxia (52 greater than or equal to PaO2 greater than or equal to 11 mm Hg). In synaptosomes isolated from the forebrain of animals submitted to moderate degrees of hypoxia, the trend of delta delta G was quite similar to that observed in normoxia. In synaptosomes isolated from the forebrain of rats submitted to severe degrees of hypoxia, the delta delta G was markedly altered as function of both aging and severity of hypoxemia. The extensive delta delta G changes were largely supported by alteration of the phosphorylation state of adenine nucleotides. However, in synaptosomes from severely hypoxic rats, aging affected the redox state, too.

Action of L-acetylcarnitine on different cerebral mitochondrial populations from hippocampus

The maximal rate (Vmax) of some mitochondrial enzymatic activities related to the energy transduction (citrate synthase, malate dehydrogenase, NADH cytochrome c reductase as total, cytochrome oxidase) and amino acid metabolism (glutamate dehydrogenase) were evaluated in non-synaptic (free) and synaptic mitochondria from rat brain hippocampus. Three types of mitochondria were isolated from rats subjected to single i.m. treatment with L-acetylcarnitine (308 mg X kg-1) or to sub-chronic i.m. treatment with L-acetylcarnitine at three different dose levels (38; 154; 614 mg X kg-1, 5 days a week, for 4 weeks). With respect to the enzymatic pattern of three types of non-synaptic and synaptic mitochondria, in hippocampus a different maximal rate of both total NADH-cytochrome c reductase and cytochrome oxidase was observed, these activities being lower in "synaptic heavy" mitochondrial subfraction rather than that in both "free" and "synaptic light" ones. This confirms that in various types of brain mitochondria a different metabolic machinery exists. Acute treatment with L-acetylcarnitine decreased citrate synthase and glutamate dehydrogenase activities only in mitochondria obtained from synaptosomes. The sub-chronic treatment with L-acetylcarnitine decreased the activity of citrate synthase and total NADH-cytochrome c reductase activities only in the same type of mitochondria, i.e. synaptic mitochondria. Therefore in vivo administration of L-acetylcarnitine mainly affects some specific enzyme activities (suggesting a specific molecular trigger mode of action) of the intrasynaptic mitochondria (suggesting a specific subcellular trigger site of action).

Modification of the skeletal muscle energy metabolism induced by intermittent normobaric hypoxia and treatment with biological pyrimidines

Muscular glycolytic fuels, intermediates and end-products (glycogen, glucose, glucose-6-phosphate, pyruvate, lactate), Krebs cycle intermediates (citrate, alpha-ketoglutarate, succinate, malate), related free amino acids (glutamate, alanine), ammonia, energy store (creatine phosphate), energy mediators (ATP, ADP, AMP) and energy charge potential were evaluated. Furthermore the maximum rate (Vmax) of the following enzyme activities was evaluated in the crude extract and/or mitochondrial fraction: for the anaerobic glycolytic pathway: hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase; for the tricarboxylic acid cycle: citrate synthase, malate dehydrogenase; for the electron transfer chain: total NADH cytochrome c reductase, cytochrome oxidase. The rat gastrocnemius muscles were analysed in normoxia and after normobaric intermittent hypoxia (12 hours continuously daily; for 5 days). Cytidine and/or uridine were administered daily at the dose of 120 mg/kg, i.p., 30 min before the beginning of the experimental hypoxia. The intermittent normobaric hypoxia induced a biochemical adaptation characterized by the decrease of the muscular contents of creatine phosphate, citrate, alpha-ketoglutarate and glutamate. This adaptation occurred in the absence of significant changes in the Vmax of the tested muscle enzymes. In gastrocnemius muscle from hypoxic rats, the two biological pyrimidines tested induced various discrete, but often related, modifications of the contents of some Krebs cycle intermediates (i.e., alpha-ketoglutarate, malate) and related free amino acids (i.e., glutamate, alanine). In any case, the treatment with cytidine and/or uridine did not modify the Vmax of marker enzymes related to energy transduction.

Adaptation of skeletal muscle energy metabolism to repeated hypoxic-normoxic exposures and drug treatment

Muscular glycolytic fuels, intermediates and end-products (glycogen, glucose, glucose-6-phosphate, pyruvate, lactate), Krebs cycle intermediates (citrate, alpha-ketoglutarate, succinate, malate), related free amino acids (glutamate, alanine), ammonia, energy store (creatine phosphate), energy mediators (ATP, ADP, AMP) and energy charge potential were evaluated. Furthermore the maximum rate (Vmax) of the following muscular enzyme activities was evaluated in the crude extract and/or mitochondrial fraction: for the anaerobic glycolytic pathway: hexokinase, phosphofructokinase, pyruvate kinase, lactate dehydrogenase; for the tricarboxylic acid cycle: citrate synthase, malate dehydrogenase; for the electron transfer chain: total NADH cytochrome c reductase, cytochrome oxidase. The rat gastrocnemius muscles were analyzed in normoxia and after repeated, alternate hypoxic and normoxic exposures (12 hours of hypoxia daily; for 5 days). Naftidrofuryl was administered daily at three different doses: 10, 15 and 22.5 mg/kg i.m., 30 min before the beginning of the experimental hypoxia. The biochemical adaptation to intermittent normobaric hypoxic-normoxic exposures was characterized by the decrease of the muscular contents of creatine phosphate, citrate, alpha-ketoglutarate and glutamate. This adaptation occurred in absence of significant changes in the Vmax of the muscle enzymes tested. By naftidrofuryl treatment, in gastrocnemius muscle from hypoxic rats both alpha-ketoglutarate and creatine phosphate contents maintained normal values, while glutamate concentration remained reduced to subnormal values. With the exception of hexokinase, naftidrofuryl treatment did not modify the Vmax of marker enzymes related to energy transduction.

Role of drugs in recovery of metabolic function of rat brain following severe hypoglycemia

Severe hypoglycemia with isoelectric EEG induced extensive deterioration of the energy state and gross alteration of amino acid contents on the rat cerebral and cerebellar cortex. During recovery, tissue glucose concentration returned to normal, while both lactate and pyruvate concentrations increased to above normal. In the recovery period, the ATP concentration increased but the adenine nucleotide pool remained reduced, even if the ADP and AMP contents were close to normal. Phosphocreatine was restored to normal concentration with reciprocal changes in creatine content. During recovery there was a rise in glutamate and glutamine concentrations, gamma-aminobutyrate content returning to normal value. Ammonia and aspartate decreased below normal, while alanine increased above normal. The effect of some pharmacological agents on the posthypoglycemic recovery was tested: (a) Ergot alkaloids (dihydroergocristine, dihydroergocriptine, dihydroergocornine); (b) Vinca minor alkaloids (vincamine TPS, (-) eburnamonine); (c) Rauwolfia serpentina alkaloids (reserpine, raubasine); (d) synthetic agent (piracetam). During the posthypoglycemic recovery, these different agents exhibited different, or even contrasting, interferences on glycolytic metabolites, amino acids and energy-rich phosphates. The metabolic alterations in the cerebellar cortex were qualitatively of the same character of those in neocortex. However, the metabolic alterations were less extensive and more sensitive to drug action.

Recovery period after profound hypoglycemia. Influence of some metabolic modulators on the cerebral endogenous substrate utilization

The content of "energy-rich" phosphates was markedly decreased in rat cerebral cortex after 20 min of severe hypoglycemia, followed by partial restitution during the recovery period. The adenine nucleotide pool remained reduced even if the energy charge returned to normal. During hypoglycemia the non-glucose endogenous substrates were provided by glycolytic intermediates, by Krebs' cycle intermediates and by related amino acids. Other substrates for brain oxidation were provided by the breakdown of phospholipids and fatty acids. After a 20 min period of post-hypoglycemic recovery, partial restoration of carbohydrates and amino acids occurred, the amino acid pool size being still reduced. The alterations in phospholipids and fatty acids persisted, while there was a tendency towards normalization of the free fatty acid cerebral content. During the post-hypoglycemic recovery, treatment with some specific metabolic modulators (i.e., uridine, L-acetylcarnitine, hopantenate, 6-amino-nicotinamide) suggests the possibility of an alternative cerebral substrate utilization due to the modulation of the cerebral biochemical machinery. Thus, increased carbohydrate utilization by hopantenate was consistent with decreased lipid breakdown, while increased carbohydrate utilization by uridine was concomitant with decreased amino acid degradation. On the other hand, decreased cerebral carbohydrate utilization by 6-aminonicotinamide was concomitant with increased lipid and amino acid breakdown. Furthermore, the increased loss of cerebral phospholipids and fatty acids by L-acetylcarnitine occurred in the presence of a large glucose availability and was concomitant with an extensive reduction on cerebral glycolytic flux.

Effect of hypoxia and pharmacological treatment on some enzyme activities in dog brain areas

The effects of nicergoline on changes in enzymatic activities induced by hypoxia and post-hypoxic recovery were studied in various brain areas of young-adult and mature Beagle dogs. In different fractions (homogenate in toto, purified mitochondria, crude synaptosomes, SM1 and SM2 synaptic mitochondria) the maximal rate (Vmax) was investigated of the more representative enzymatic activities of: a) glycolysis, b) Krebs' cycle, c) electron transfer chain, d) amino acid and acetylcholine metabolism, e) lysosomal function. The physiopathological conditions caused alterations in different enzymatic activities depending on the area and subfraction investigated. Nicergoline tended to antagonize some of these alterations. Its action was mainly on non-synaptic mitochondria by a "braking" effect on some key enzyme activities of mitochondrial metabolism (i.e. citrate synthase, cytochrome oxidase and glutamate dehydrogenase) which suggests a sparing action in the brain.

Cerebral and cerebellar metabolic changes induced by drugs during the recovery period after profound hypoglycemia

On rat cerebral and cerebellar cortex, severe hypoglycemia with isoelectric EEG induced extensive deterioration of the energy state and gross alteration of amino acid contents. During recovery, tissue glucose concentration returned to normal, while the rate of glycogen synthesis was slow, both lactate and pyruvate concentrations increasing to above normal. In the recovery period, the ATP concentration increased but the adenine nucleotide pool remained reduced, even if the ADP and AMP contents were close to normal. Phosphocreatine was restored to normal concentrations with reciprocal changes in creatine content. During recovery there was a rise in glutamate and glutamine concentrations, gamma-aminobutyrate content returning to normal value. Ammonia and aspartate decreased below normal, while alanine increased above normal. The effect of some drugs on the post-hypoglycemic recovery was tested: (a) Ergot alkaloids (dihydroergocristine, dihydroergocriptine, dihydroergocornine); (b) Vinca minor alkaloids (vincamine TPS, (--)-eburnamonine); (c) Rauwolfia serpentina alkaloids (reserpine, raubasine); (d) synthetic agent (piracetam). During the post-hypoglycemic recovery, these different agents exhibited different, or even contrasting, interferences on glycolytic metabolites, amino acids and energy-rich phosphates. The metabolic alterations in the cerebellar cortex were qualitatively of the same character of those in neocortex. However the metabolic alterations were less extensive and more sensitive to drug action.

Cerebral endogenous substrate utilization during the recovery period after profound hypoglycemia

Markedly decreased levels of energy-rich phosphates were seen in cerebral cortex after severe hypoglycemia, followed by their partial restitution during the recovery period. During hypoglycemia the nonglucose endogenous substrates were provided by glycolytic intermediates, by Krebs cycle intermediates, and by related amino acids. Other potential substrates for brain oxidation were provided by the breakdown of phospholipids and fatty acids. After a 20-min period of posthypoglycemic recovery, partial restoration of carbohydrates and amino acids occurred, although the amino acid pool size was still reduced. The alterations in phospholipids and fatty acids persisted, while there was a tendency toward normalization of the free fatty acid content. During the posthypoglycemic recovery, treatment with some specific metabolic modulators (6-aminonicotinamide, hopantenate, uridine, L-acetylcarnitine) suggested the possibility of an alternative cerebral substrate utilization owing to modulation of the cerebral biochemical machinery. Thus, increased carbohydrate utilization by hopantenate was consistent with decreased lipid breakdown, while increased carbohydrate utilization by uridine was concomitant with decreased amino acid degradation. In this way, decreased cerebral carbohydrate utilization by 6-amino-nicotinamide was associated with increased lipid and amino acid breakdown. Furthermore, the increased loss of cerebral phospholipids and phospholipid-bound fatty acids by L-acetylcarnitine occurred in the presence of a large glucose availability and was associated with an extensive reduction of cerebral glycolytic flux.

Synaptic and non-synaptic mitochondria from rat cerebral cortex. Characterization and effect of pharmacological treatment on some enzyme activities related to energy transduction

By a cellular subfractionation technique, synaptic and non-synaptic mitochondria from a single rat cerebral cortex were obtained. In these different mitochondrial populations the activity of citrate synthase, malate dehydrogenase, total NADH-cytochrome c reductase, cytochrome oxidase and glutamate dehydrogenase were evaluated. Except for glutamate dehydrogenase, the enzyme specific activities evaluated in the "free" mitochondrial fraction were higher than those evaluated in the "synaptic" SM1 and SM2 mitochondrial fractions, the differences between SM1 and SM2 fractions being significant. The effect of the in vivo administration of naftidrofuryl given at different doses and at different times was studied. The treatment induced few but different changes in the various mitochondrial populations.

Recovery after hypoglycemic brain injury. Action of some biological substances on the cerebral metabolism

In artificially ventilated beagle dogs a severe hypoglycemic condition was induced by insulin injection, while the posthypoglycemic recovery was induced by glucose treatment at the end of a 20-min period of spontaneous electroencephalographic silence. The motor area of the cerebral cortex was analyzed for glycolytic metabolites, related amino acids, energy mediators, fatty acids, phospholipids and free fatty acids. The effects on the posthypoglycemic recovery of a intracarotid infusion with some agents (i.e. uridine, cytidine, DL-carnitine, DL-acetylcarnitine, papaverine) were tested. Severe hypoglycemia induced an extensive derangement of the brain metabolism, with partial restitution during the posthypoglycemic recovery. During this condition, the intracarotid perfusion with some biological pyrimidines (uridine, cytidine) interfered with the glycolytic and amino acid metabolites, inducing a decrease in glucose, pyruvate and lactate contents, and an increase in succinate, alanine and glutamine cerebral concns. The lipid carriers (DL-carnitine, DL-acetylcarnitine) interfered with the fatty acid degradation inducing a magnification of the decrease in the individual (palmitic acid, oleic acid) and total fatty acids, the vasodilating agent (papaverine) being practically inactive.

Rat cortex synaptic and nonsynaptic mitochondria: enzymatic characterization and pharmacological effects of naftidrofuryl

In order to investigate the in vivo pharmacological effects of the drug naftidrofuryl, we prepared populations of synaptic and nonsynaptic mitochondria from rat brain cortex. In these different mitochondrial populations the activities of citrate synthase, malate dehydrogenase, total NADH cytochrome c reductase, cytochrome oxidase, and glutamate dehydrogenase were evaluated. Except for glutamate dehydrogenase, the specific activities of the enzymes evaluated in the "free" mitochondrial fraction were higher than those observed in the "synaptic" SM1 and SM2 mitochondrial fractions, the difference between SM1 and SM2 fractions being significant. The in vivo administration of naftidrofuryl induced few and different changes in the various mitochondrial populations.

Acetylcholine esterase sensitivity to chronic administration of diphenylhydantoin and effects on cerebral enzymatic activities related to energy metabolism

The effect of chronic treatment (8 months) with diphenylhydantoin (DPH) on rat brain was studied. The activity of some enzymes related to energy transduction (lactate dehydrogenase, citrate synthase, and malate dehydrogenase; NADH-cytochrome c reductase and cytochrome oxidase) and neurotransmission (acetylcholine esterase) was evaluated both in the whole brain homogenate and/or in the crude mitochondrial fraction. A clear-cut decrease of acetylcholine esterase activity was observed, the decrease continuing even after treatment was discontinued. Effects on energy metabolism and on lactate dehydrogenase, malate dehydrogenase, and cytochrome oxidase are discussed.