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At least 19 recordsLinked to original sources
PubMed2005

Placebo-controlled double-blind randomized trial on the use of L-carnitine, L-acetylcarnitine, or combined L-carnitine and L-acetylcarnitine in men with idiopathic asthenozoospermia.

OBJECTIVE: To evaluate the effectiveness of L-carnitine (LC) or L-acetyl-carnitine (LAC) or combined LC and LAC treatment in improving semen kinetic parameters and the total oxyradical scavenging capacity in semen. DESIGN: Placebo-controlled, double-blind, randomized trial. SETTING: Andrology unit, Department of Internal Medicine, Polytechnic University of Marche, Italy. PATIENT(S): Sixty infertile men, ages 20 to 40 years, with the following baseline sperm selection criteria: concentration > 20 x 10(6)/mL, sperm forward motility < 50%, and normal sperm morphology > 30%; 59 patients completed the study. INTERVENTION(S): Patients underwent a double-blind therapy of LC 3 g/d, LAC 3 g/d, a combination of LC 2 g/d and LAC 1 g/d, or placebo. The study design was 1 month of run in, 6 months of therapy or placebo, and 3 months of follow-up evaluation. MAIN OUTCOME MEASURE(S): Variations in semen parameters used for patient selection, and variations in total oxyradical scavenging capacity of the seminal fluid. RESULT(S): Sperm cell motility (total and forward, including kinetic features determined by computer-assisted sperm analysis) increased in patients to whom LAC was administered both alone or in combination with LC; combined LC + LAC therapy led to a significant improvement of straight progressive velocity after 3 months. The total oxyradical scavenging capacity of the semen toward hydroxyl and peroxyl radicals also increased and was positively correlated with the improvement of kinetic features. Patients with lower baseline values of motility and total oxyradical scavenging capacity of the seminal fluid had a significantly higher probability of responding to the treatment. CONCLUSION(S): The administration of LC and LAC is effective in increasing sperm kinetic features in patients affected by idiopathic asthenozoospemia and improves the total oxyradical scavenging capacity of the seminal fluid in the same population.

Acetylcarnitine↗
PubMed1982

Urinary excretion of acetylcarnitine during human diabetic and fasting ketosis.

The urinary excretion of acetylcarnitine was studied in patients with diabetic ketosis before and during insulin therapy and in normal-weight and obese subjects during fasting. In the diabetic ketotic patients, acetylcarnitine represented 61% of the total acylcarnitine excretion. During the first 24 h of insulin treatment, acetylcarnitine excretion decreased and on the 5th day of treatment was 18% of the acylcarnitines excreted. The urinary excretion of the other acylcarnitines fell slowly. In normal-weight subjects fasted for 3 days, the urinary excretion of acetylcarnitine increased on the 2nd day of fasting, and on the 3rd day acetylcarnitine accounted for 78% of the excreted acylcarnitine. In obese subjects there was a progressive increase in urinary acetylcarnitine excretion, but on day 6 it represented only 55% of the total acylcarnitine excreted. The urinary excretion of acetylcarnitine correlated with blood beta-hydroxybutyrate concentration in the normal-weight subjects during fasting and in the diabetic ketotic patients. Acetylcarnitine accounts for a major fraction of the acylcarnitines excreted in the three ketotic conditions studied. The contribution of acetylcarnitine to the change in acylcarnitines as ketosis appears or disappears is significantly less in the obese subjects than in the normal-weight subjects or in the diabetic patients. This difference may reflect an alteration in the production or disposition of acetyl-CoA and acetylcarnitine in obesity.

Acetylcarnitine↗
PubMed1992

Alterations of urinary acetylcarnitine in valproate-treated rats: the effect of L-carnitine supplementation.

Urinary excretion of acetylcarnitine was measured by high-performance liquid chromatography in two experimental groups of valproate-treated rats. In the urine of mature rats weighing 180 to 200 g treated with valproate (500 mg/kg/day), acetylcarnitine levels were higher than those in controls on days 4 and 7, while L-carnitine-supplemented rats showed lower levels than the valproate group. The valproate-treated rats showed an increased acetylcarnitine/acylcarnitine ratio on and after day 4, while the L-carnitine-supplemented rats showed no significant change compared to the controls on any days. In the urine of immature rats weighing 80 to 90 g treated with valproate (50 mg/kg/day), acetylcarnitine levels were increased after the 14th day of treatment. These results suggest that an increase in urinary acetylcarnitine occurs when small doses of valproate are administered for a longer time. We speculate that increased acetylcarnitine is not a product of beta-oxidation in mitochondria, because L-carnitine supplementation decreases the acetylcarnitine levels. Although the mechanism of acetylcarnitine excretion during valproate administration is not clear, L-carnitine supplementation is effective in decreasing the level of urinary acetylcarnitine and keeping the acetylcarnitine/acylcarnitine ratio normal.

Acetylcarnitine↗
PubMed1990

Partial purification and characterization of an acetylcarnitine hydrolase from bovine epididymal spermatozoa.

We previously reported that intact epididymal spermatozoa from bulls and hamsters oxidize [1-14C]acetyl-L-carnitine to 14CO2 at about the same rate as they oxidize [1-14C]acetate. In addition, we showed that acetylcarnitine is hydrolyzed by a hydrolase present in the plasma membrane and that the carnitine moiety does not enter the cell. Here we report the partial purification of the acetylcarnitine hydrolase from bovine spermatozoa and describe some of its properties. The detergent-extracted enzyme was purified by FPLC using an anion-exchange Mono-Q column. The hydrolase activity eluted from the column with the application of 0.22 to 0.30 M NaCl and was separated from acetylcholinesterase activity, which eluted with 0.35 to 0.40 M NaCl. Specific inhibitors of acetylcholinesterase had little effect on acetylcarnitine hydrolase but p-hydroxymercuriphenylsulfonate was a potent inhibitor of the hydrolase. Kinetic studies of the hydrolase yielded a K'm of 6-10 mM for acetylcarnitine and a V'max of 0.16 nmol min-1 mg protein-1. Similar studies with the acetylcholinesterase yielded a K'm for acetylcholine of about 300 microM and a V'max of 165 nmol min-1 mg protein-1. Acetylcarnitine was a poor substrate for the acetylcholinesterase. Several acyl-L-carnitines were tested as substrates for the hydrolase and the preferred substrate was acetylcarnitine. The role of acetylcarnitine hydrolase in the metabolism of acetylcarnitine by epididymal spermatozoa is discussed.

Acetylcholinesterase↗
PubMed1994

Acetylcarnitine inhibits alcohol dehydrogenase.

Carnitine and acetylcarnitine are used as dietary supplements and as therapeutic agents. Carnitine attenuates ethanol metabolism in intact animals but the in vitro activities of alcohol dehydrogenase (ADH), microsomal ethanol oxidizing system (MEOS) or catalase are not significantly altered by carnitine. Since acetylcarnitine was a far more potent inhibitor of ethanol oxidation than carnitine in hepatocytes, the activities of rat liver ADH and MEOS were determined with or without acetylcarnitine. The activity of ADH, not MEOS, was significantly inhibited by acetylcarnitine at NAD: acetylcarnitine < or = 1. The inhibition is of a competitive nature where acetylcarnitine competes with NAD+ (Ki = 135 mumol.L-1). This finding is unique in that this is the first report of this function of acetylcarnitine and it is a novel interaction between two important nutrients, niacin and carnitine.

Acetylcarnitine↗
PubMed1991

Activity of L-carnitine and L-acetylcarnitine on cholinoceptive neocortical neurons of the rat in vivo.

Carnitine and acetylcarnitine have been demonstrated to be present in the CNS and to be involved in cholinergic mechanisms, even if their exact role in neurotransmission is still unknown. This microiontophoretic study was carried out on single cholinoceptive neurons of the somatosensory cortex in the rat in order to analyze the effects of L- and D-carnitine and L-acetylcarnitine on the spontaneous firing and the neuronal responses to some putative transmitters. L-carnitine and L-acetylcarnitine increased the spontaneous discharge rate, while D-carnitine was found to be ineffective. L-acetylcarnitine clearly potentiated the cholinergic excitatory responses. On the contrary, L-carnitine was found to reduce cholinergic responses in a great percentage of units and to inhibit L-acetylcarnitine-induced excitatory responses. Atropine blocked the increase in firing rate induced by L-carnitine and L-acetylcarnitine, thus suggesting for both of them a muscarinic activity. No interactions were observed between carnitines and GABA and glutamate. These results show that carnitine and acetylcarnitine are stereospecific neuroactive compounds with a cholinomimetic activity. They may play a role in a modulatory system for the cholinoceptive cortical neuron.

Acetylcarnitine↗
PubMed1985

Stereospecific effects of acetylcarnitine on the spontaneous activity of brainstem neurones and their responses to acetylcholine and serotonin.

Acetylcarnitine is an endogenous substance, active in the CNS, but its exact role in neurotransmission is still unknown. The present study was made to analyze by means of iontophoretic administration on single neurones of the medullary-pontine reticular formation in the rat the effects of the D- and L-acetylcarnitine on spontaneous and glutamate-evoked firing and on responses to applications of some other putative transmitters, such as acetylcholine, 5-hydroxytryptamine (5-HT), gamma-aminobutyric acid (GABA) and noradrenaline. L-Acetylcarnitine increased both spontaneous and evoked discharges, and potentiated cholinergic and serotonergic responses. The D-isomer was found to be almost ineffective. Neuronal responses to L-acetylcarnitine were reduced by dihydro-beta-erythroidine and enhanced by eserine, while atropine was ineffective. L-Acetylcarnitine increased both excitatory and inhibitory responses to 5-HT and its effect on the increase in firing rate induced by serotonergic drugs was reduced by dihydro-beta-erythroidine, but not by atropine. L- and D-Acetylcarnitine did not affect GABAergic or noradrenergic transmission. These results suggest a stereospecific facilitatory action of acetylcarnitine on neuronal responses to acetylcholine and 5-HT. It is hypothesized that this action could be exerted at a presynaptic level, at least with regard to serotonergic-induced responses, and that nicotinic receptors may be involved in the synaptic mechanism of release or reuptake of both acetylcholine and 5-HT.

Acetylcarnitine↗
PubMed1992

Changes in carnitine and acetylcarnitine in human semen during cryopreservation.

L-Carnitine and acetylcarnitine concentrations were determined in spermatozoa and seminal plasma from 15 men, in both fresh ejaculate and frozen-thawed semen with cryoprotective medium. Sperm motility was also evaluated. In fresh samples, the levels of carnitine and acetylcarnitine in seminal plasma were comparable whereas in spermatozoa, acetylcarnitine predominated. Cryopreservation did not change the carnitine and acetylcarnitine levels in seminal plasma nor the carnitine concentration in spermatozoa; by contrast, the acetylcarnitine level in spermatozoa was decreased in 14 cases (110 +/- 8 versus 210 +/- 20 nmol/10(8) cells). This decrease in acetylcarnitine content was greater during semen dilution in cryoprotectant than after the freezing/thawing process. Motility was also decreased in all cases after the freezing/thawing process. These results suggest that acetylcarnitine recovery in spermatozoa is further evidence of the deleterious effect of the cryoprotective medium in the cryopreservation of semen.

Acetylcarnitine↗
PubMed1989

The metabolism of acetylcarnitine and acetate by bovine and hamster epididymal spermatozoa.

Since acetylcarnitine has been identified in the epididymal plasma of many mammalian species, we investigated whether acetylcarnitine could serve as an energy substrate for epididymal bull and hamster spermatozoa. Intact caudal cells from both species oxidized [I-14C]acetyl-l-carnitine to 14CO2, in vitro, and the amount oxidized was dependent on time, substrate concentration, and cell number. Within each species, the rate of oxidation was the same as the rate at which free [1-14C]acetate was oxidized. Spermatozoa incubated with [3H]acetyl-L-carnitine hydrolyzed the compound and [3H]acetate accumulated in the medium. Unlabeled acetate added to the incubation medium competed with cellular uptake of [3H]acetate and resulted in further increase in [3H]acetate accumulation in the medium. Furthermore, the acetyl group of acetylcarnitine was oxidized by spermatozoa without concomitant uptake of the carnitine group. Purified plasma membrane vesicles contained an acetylcarnitine hydrolase activity that was solubilized from whole cells by detergents and that could be distinguished from acetylcholinesterase also present in the cells. The solubilized acetylcarnitine hydrolase activity was inhibited by p-hydroxymercuriphenylsulfonate, but not by the specific acetylcholinesterase inhibitors, eserine or BW63C47. The sulfhydryl blocker also inhibited the production of 14CO2 from [1-14C]acetylcarnitine by intact cells; acetylcholinesterase inhibitors did not. From estimates of sperm energy requirements, our results indicate that extracellular acetylcarnitine serves as a physiologically important energy substrate for maturing sperm cells.

Acetates↗
PubMed1990

Association between muscle acetyl-CoA and acetylcarnitine levels in the exercising horse.

Treadmill exercise of 2-min duration and increasing intensity resulted in increased formation of acetyl-CoA and acetylcarnitine in working muscle of Thoroughbred horses. At high work intensities a plateau was reached for both acetyl-CoA (approximately 50 mumols/kg dry muscle) and acetylcarnitine (approximately 20 mmol/kg dry muscle). Postexercise concentrations were significantly (P less than 0.001) correlated; [acetylcarnitine] = 349.[acetyl-CoA] + 2.4. The results indicate that approximately 350 mumols acetylcarnitine were accumulated for every 1 mumol acetyl-CoA. Under the conditions of exercise used it is probable that most of the acetyl-CoA formed is generated through the intramitochondrial decarboxylation of pyruvate. The acetyl groups of acetyl-CoA are apparently redistributed throughout the whole cell through formation of acetylcarnitine, which readily transverses the mitochondrial membrane. Despite the redistribution, however, the close correlation between acetylcarnitine and acetyl-CoA would indicate that equilibrium was maintained and that neither acetylcarnitine transferase nor carnitine/acetylcarnitine translocase were rate limiting. There is some question as to whether the changes observed relate directly to exercise itself or to the state in muscle 10 s or more after exercise.

Acetyl Coenzyme A↗
PubMed1965

Stimulation of oxidation of mitochondrial fatty acids and of acetate by acetylcarnitine.

1. Acetylcarnitine added in catalytic amounts to kidney mitochondria produces an active oxidation of endogenous fatty acids. 2. In conditions of mitochondrial ;aging', under which acetate is not oxidized, acetylcarnitine also promotes the oxidation of this exogenous substrate. 3. Dinitrophenol completely abolishes the action of acetylcarnitine. 4. Carnitine is ineffective both in the oxidation of endogenous fatty acids and of exogenous acetate. 5. The action of acetylcarnitine is shared, though to a smaller extent, by pyruvate. 6. The mechanism of acetylcarnitine action has been interpreted by considering that the readily oxidizable acetyl group of acetylcarnitine can supply the initial investment of energy needed to start fatty acid oxidation.

Acetates↗
PubMed1993

Is Acetylcarnitine a Substrate for Fatty Acid Synthesis in Plants?

Long-chain fatty acid synthesis from [1-14C]acetylcarnitine by chloroplasts isolated from spinach (Spinacia oleracea), pea (Pisum sativum), amaranthus (Amaranthus lividus), or maize (Zea mays) occurred at less than 2% of the rate of fatty acid synthesis from [1-14C]acetate irrespective of the maturity of the leaves or whether the plastids were purified using sucrose or Percoll medium. [1-14C]-Acetylcarnitine was not significantly utilized by highly active chloroplasts rapidly prepared from pea and spinach using methods not involving density gradient centrifugation. [1-14C]Acetylcarnitine was recovered quantitatively from chloroplast incubations following 10 min in the light. Unlabeled acetyl-L-carnitine (0.4 mM) did not compete with [1-14C]acetate (0.2 mM) as a substrate for fatty acid synthesis by any of the more than 70 chloroplast preparations tested in this study. Carnitine acetyltransferase activity was not detected in any chloroplast preparation and was present in whole leaf homogenates at about 0.1% of the level of acetyl-coenzyme A synthetase activity. When supplied to detached pea shoots and detached spinach, amaranthus, and maize leaves via the transpiration stream, 1 to 4% of the [1-14C]acetylcarnitine and 47 to 57% of the [1-14C]acetate taken up was incorporated into lipids. Most (78-82%) of the [1-14C]acetylcarnitine taken up was recovered intact. It is concluded that acetylcarnitine is not a major precursor for fatty acid synthesis in plants.

Journal Article↗
PubMed1995

Quantification of carnitine, acetylcarnitine, and total carnitine in tissues by high-performance liquid chromatography: the effect of exercise on carnitine homeostasis in man.

A method for the quantitative determination of carnitine, acetylcarnitine, and total carnitine in tissue was developed for application to clinical research and diagnosis. Human skeletal muscle and heart specimens (10-20 mg) were homogenized in 1 ml of water. Aliquots of the resulting homogenates (50 microliters) were extracted with 1.0 ml of acetonitrile:methanol (3:1) and the carnitine-related compounds were isolated using columns containing 300 mg of silica gel. Samples were then derivatized with 4'-bromophenacyl trifluoromethanesulfonate for spectrophotometric detection or 2-(2,3-naphthalimino)ethyl trifluoromethanesulfonate for fluorescence detection and quantified by high-performance liquid chromatography. Fluorometric detection of 2-(2,3-naphthalimino)ethyl ester derivatives afforded a 500-fold increase in sensitivity when compared to derivatization with 4'-bromophenacyl trifluoromethanesulfonate. This methodology permitted detection of acetylcarnitine in dilute human muscle homogenates at quantities of 790 fmol of acetylcarnitine injected. The method was applied to a series of human skeletal muscle biopsy samples obtained from subjects performing exercise at high work loads. The method permitted quantification of carnitine, acetylcarnitine, and total carnitine (sum of carnitine and all acylcarnitines) and demonstrated the specific redistribution of the carnitine pool from carnitine to acetylcarnitine with exercise above the lactate threshold. This HPLC method is facile, and provides a sensitive and specific approach for use in human biopsy specimens.

Acetophenones↗
PubMed2002

Brain regions involved in fatigue sensation: reduced acetylcarnitine uptake into the brain.

Fatigue is an indispensable sense for ordering rest. However, the neuronal and molecular mechanisms of fatigue remain unclear. Chronic fatigue syndrome (CFS) with long-lasting fatigue sensation seems to be a good model for studying these mechanisms underlying fatigue sensation. Recently, we found that most patients with CFS showed a low level of serum acetylcarnitine, which well correlated with the rating score of fatigue, and that a considerable amount of acetyl moiety of serum acetylcarnitine is taken up into the brain. Here we show by metabolite analysis of the mouse brain that an acetyl moiety taken up into the brain through acetylcarnitine is mainly utilized for the biosynthesis of glutamate. When we studied the cerebral uptake of acetylcarnitine by using [2-(11)C]acetyl-L-carnitine in 8 patients with CFS and in 8 normal age- and sex-matched controls, a significant decrease was found in several regions of the brains of the patient group, namely, in the prefrontal (Brodmann's area 9/46d) and temporal (BA21 and 41) cortices, anterior cingulate (BA24 and 33), and cerebellum. These findings suggest that the levels of biosynthesis of neurotransmitters through acetylcarnitine might be reduced in some brain regions of chronic fatigue patients and that this abnormality might be one of the keys to unveiling the mechanisms of the chronic fatigue sensation.

Acetylcarnitine↗
PubMed1990

Changes in muscle free carnitine and acetylcarnitine with increasing work intensity in the Thoroughbred horse.

Treadmill exercise in Thoroughbred horses of 2 min duration and increasing intensity resulted in increased formation and accumulation of acetylcarnitine in the working middle gluteal muscle. At high work intensities a plateau in acetylcarnitine formation was reached corresponding to approximately 70% of the total carnitine pool (approx. 30 mmol.kg-1 dry muscle). Formation of acetylcarnitine was mirrored by an equal fall in the free carnitine content, which stabilised, at the highest work intensities, at around 8 mmol.kg-1 dry muscle. Acetylcarnitine and carnitine reached their point of maximum change at a work intensity just below that resulting in the rapid production and accumulation of lactate and glycerol 3-phosphate. It is possible that the formation of acetylcarnitine is important in the regulation of the intramitochondrial acetyl CoA/CoA ratio; equally these changes may represent a blocking mechanism aimed at preventing the transfer of unwanted free fatty acids (as acylcarnitines) into the mitochondria at work intensities where they could contribute little to energy production.

Acetylcarnitine↗
PubMed1989

Effects of L-carnitine, L-acetylcarnitine and gangliosides on the regeneration of the transected sciatic nerve in rats.

Three pharmacological agents, L-carnitine, L-acetylcarnitine and gangliosides, were tested for their ability to enhance the regeneration of the rat sciatic nerve following transection and microsurgical repair. The drugs were administered intraperitoneally at the dose of 50 mg/kg/d for 28 and 56 d postoperatively. At the end of treatment, the motor function recovery of the peroneal component of the sciatic nerve was assessed and the regenerated nerves were analysed morphometrically on histological semi-thin sections. Also, the reinnervated extensor digitorum longus (EDL) muscles were studied histochemically using the adenosine-triphosphatase (ATP-ase) technique 56 d after surgery. Motor function assessment at 56 d after nerve repair revealed that L-acetylcarnitine-treated animals recovered a clinical grade significantly higher (p less than 0.05) than the control animals. Twenty-eight days after nerve repair, the number of myelinated fibres was significantly higher (p less than 0.05) in L-acetylcarnitine and ganglioside-treated animals than in control animals. However, 56 d after nerve repair the number of regenerated fibres in all the drug-treated groups was not significantly different from that of the control group. The EDL muscles of the drug-treated animals did not show significant differences from those of control animals with respect to fibre composition and fibre diameter although the L-acetylcarnitine-treated animals exhibited a significantly lower (p less than 0.05) degree of muscle atrophy than did the control animals. The results of the present work seem to indicate that L-acetylcarnitine and to a lesser extent gangliosides exert some favourable effect on the regeneration of the transected sciatic nerve in rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcarnitine↗
PubMed2002

Carbohydrate ingestion reduces skeletal muscle acetylcarnitine availability but has no effect on substrate phosphorylation at the onset of exercise in man.

This study investigated the effect of reduced acetylcarnitine availability on oxidative metabolism during the transition from rest to steady-state exercise. Eight male subjects completed two randomised exercise trials at 68 % of the peak rate of O(2) uptake (V((O(2)),peak)). On one occasion subjects ingested 1 g (kg body mass)(-1) glucose 75 min prior to exercise (CHO), whereas the other trial acted as a control (CON). Muscle samples were obtained pre- and 75 min post-ingestion, and following 1 and 10 min of exercise. Plasma glucose and insulin were elevated (P < 0.05), and plasma free fatty acids (FFA) were lower at the onset of exercise in CHO. Acetylcarnitine (CON, 4.8 +/- 1.8; CHO, 1.5 +/- 0.9 mmol (kg dry mass (d.m.))(-1), P < 0.05) and acetyl CoA (CON, 13.2 +/- 2.3; CHO, 6.3 +/- 0.6 micromol (kg d.m.)(-1), P < 0.05) were lower at rest, whereas pyruvate dehydrogenase activation (PDHa) was greater in CHO compared with CON (CON, 0.78 +/- 0.07; CHO, 1.44 +/- 0.19 mmol min(-1) (kg wet mass (w.m.))(-1)). Respiratory exchange ratio (RER) was significantly elevated during exercise in CHO. The acetyl groups increased at similar rates at the onset of exercise (1 min) and there was no difference in substrate phosphorylation as determined from lactate accumulation and phosphocreatine degradation between trials. Subsequently, oxidative metabolism during the transition from rest to steady-state exercise was not affected by prior carbohydrate ingestion. Although exercise resulted in the rapid activation of PDH in both trials, PDHa was greater at 1 min in CHO (CON, 2.36 +/- 0.22; CHO, 2.91 +/- 0.18 mmol min(-1) (kg w.m.)(-1)). No differences in muscle metabolite levels and PDHa were observed after 10 min of moderate exercise between trials. In summary, at rest, carbohydrate ingestion induced multiple metabolic changes which included decreased acetylcarnitine availability and small increases in PDHa. The prior changes in PDHa and acetylcarnitine availability had no effect on substrate phosphorylation and oxidative metabolism at the onset of exercise. These data suggest that acetylcarnitine availability is unlikely to be the site of metabolic inertia during the transition from rest to steady-state moderate intensity exercise.

Acetyl Coenzyme A↗
PubMed1992

Effects of fat availability on acetyl-CoA and acetylcarnitine metabolism in rat skeletal muscle.

This study was designed to examine the effects of stimulation and fat availability on the contents of acetyl coenzyme A (acetyl-CoA), free CoA (CoASH), acetylcarnitine, and free carnitine in the oxidative fiber types of rat skeletal muscle. Hindlimb muscles were perfused with no exogenous free fatty acids (FFA) or high FFA (0.93 +/- 0.03 mM) for 10 min at rest and during isometric, tetanic stimulation. Soleus (SOL) and red gastrocnemius (RG) muscles were sampled prior to perfusion and following rest perfusion and 1 and 5 min of stimulation. The SOL muscle contains predominantly slow oxidative (SO) fibers and the RG contains 56% fast oxidative-glycolytic (FOG) and 35% SO fibers. O2 uptake and tetanic tension production were similar in the fat-free and high FFA treatments. Rest perfusion with high FFA increased acetyl-CoA from 14.6 +/- 1.0 to 20.1 +/- 2.5 nmol/g dry muscle (dm) and acetylcarnitine from 0.12 +/- 0.01 to 0.78 +/- 0.18 mumol/g dm in the RG, while fat-free perfusion had no effect. The SOL results were similar as high FFA increased acetyl-CoA from 7.7 +/- 1.0 to 14.2 +/- 3.1 nmol/g dm and acetylcarnitine from 0.14 +/- 0.02 to 0.49 +/- 0.09 mumol/g dm. Stimulation increased acetyl-CoA and acetylcarnitine to values above rest in SOL and RG in both treatments and removed all fat-free and high-fat differences. The decreases in CoASH and free carnitine were reciprocal to the increases in acetyl-CoA and acetylcarnitine at all time points in both muscles such that total CoA and carnitine were constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyl Coenzyme A↗