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At least 19 recordsLinked to original sources
PubMed1977

Urinary excretion of carnitine and serum concentrations of carnitine and lipids in patients with hypofunctional endocrine diseases: involvement of adrenocorticoid and thyroid hormones in ACTH-induced augmentation of carnitine and lipids metabolism.

The promoting effect of ACTH on carnitine and lipid metabolism was studied in patients with various endocrine hypofunctions. The results were compared with those of normal subjects. In adrenocortical insufficiency, hypothyroidism and hypopituitarism urinary excretion of carnitine was significantly lower than in normal subjects. On intramuscular injection of synthetic beta1-24 ACTH-Z urninary excretion of carnitine in normal subjects increased sixfold on the day of the injection and returned to the pretreatment level on the third day. Serum concentrations of carnitine and FFA increase in parallel with carnitine excretion, while serum triglyceride was lowered in response to ACTH administration. These responses were totally lacking or substantially suppressed in patients with the above endocrine insufficiencies. In hypothyroid and hypopituitary patients substitution therapy restored the responses to ACTH in the same fashion as those in normal subjects. These findings suggest that the promoting effect of ACTH on carnitine and lipid metabolism requires the presence of intact adrenocortical and thyroid functions.

Addison Disease↗
PubMed1979

Carnitine, acetylcarnitine and the activity of carnitine acyltransferases in seminal plasma and spermatozoa of men, rams and rats.

The concentration of total carnitine (i.e. carnitine plus acetylcarnitine) was measured in seminal plasma and spermatozoa of men and rams. In ram semen, there was a close correlation between the concentration of spermatozoa and that of total carnitine in the seminal plasma, indicating that the epididymal secretion was the sole source of seminal carnitine. The percentage of total carnitine present as acetylcarnitine was 40% in seminal plasma and 70-80% in spermatozoa. The acetylation state of carnitine in seminal plasma was apparently not influenced by the metabolic activity of spermatozoa in ejaculated ram semen as no change was found in the plasma concentration of carnitine or acetylcarnitine up to 45 min after ejaculation. In spermatozoa, the activity of carnitine acetyltransferase (EC 2.3.1.7) was approximately equivalent to that of carnitine palmitoyltransferase (EC 2.3.1.21); and the activity of these enzymes was similar in ram and human spermatozoa but greater in rat spermatozoa. It is concluded that there is no correlation between the content of either total carnitine or the carnitine acyltransferases and the respiratory capacity of spermatozoa.

Acetylcarnitine↗
PubMed1979

Transport of L-carnitine induced by prednisolone in an established cell line (CCL 27). A possible explanation of the therapeutic effect of glucocorticoids in muscular carnitine deficiency syndrome.

Prednisolone (10(-8)--10(-5) mol/l) in the growth medium for 24 h increased the rate of uptake of L-[3H]carnitine in an established cell line (CCL 27) to 164 +/- 6% (mean +/-S.E.) of the rate observed in untreated cells. At the same time the intracellular content of free L-carnitine increased about 20%. The simultaneous addition of prednisolone (10(-6) mol/l for 24 h) and L-carnitine (10(-4) mol/l for 96 h) to the growth medium increased the rate of uptake to 225 +/- 8% (mean +/-S.E.) of that in untreated cells. The increase seemed to be mediated through an increase in number of carriers, as judged by the increase in V of the transport process with unchanged Km. Phosphodiesterase I, an enzyme mainly localized in the plasma membrane, increased its activity about 3.5 times when cells were stimulated with prednisolone. Thus, it seems that the increase in the rate of uptake of L-carnitine mediated by glucocorticoids, is part of a more general effect on the plasma membrane. The observations offer an explanation to the observed clinical improvement in patients with muscular carnitine deficiency treated with glucocorticoids and/or L-carnitine.

Biological Transport↗
PubMed1979

The distribution of carnitine and acetylcarnitine in the rabbit epididymis and the carnitine content of rabbit spermatozoa during maturation.

The highest levels of carnitine and acetylcarnitine were found in the cauda, and spermatozoa from the proximal cauda contained significantly greater amounts of carnitine than those removed from the corpus or caput epididymidis. Acetylcarnitine levels (as a % of the total carnitine pool) were greater in all regions of the rabbit epididymis than has been reported in other species. It is suggested that the accumulation of carnitine is involved in sperm maturation.

Acetylcarnitine↗
PubMed1979

[Lipidic myopathy with severe cardiomyopathy caused by a generalized carnitine deficiency. Favourable course during carnitine hydrochloride treatment].

The case of a girl who presented with gastrointestinal upsets with nausea, vomiting and occasional hypoglycaemic attacks during childhood is reported. At about 5 years of age generalised muscular weakness with severe amyotrophy, cardiomegaly with a cardiothoracic ratio of 0,63, left ventricular hypertrophy on electrocardiography and left ventricular dilatation with hypokinesis on echocardiography were observed. A few weeks later she developed severe cardiac failure. Muscle biopsy showed muscular dystrophy with lipid infiltration due to carnitine deficiency )serum carnitine 9 nmoles/ml, normal values: 46 +/- 6,9 nmoles/ml; muscle carnitine 0,27 nmoles/mg, normal values: 3,0 +/- 0,79 nmoles/mg fresh frozen weight). She improved rapidly with carnitine chlorhydrate and a diet low in lipids and high in medium chain triglycerides. Regression of muscular symptoms and cardiac failure was observed. After 13 months follow-up with no tonicardiac therapy she is much improved; the signs of heart failure have disappeared, the cardiothoracic ratio is now 0,55 and the electrocardiogramme and echocardiogramme are normal.

Biopsy↗
PubMed1979

Pharmacokinetics of l-carnitine in man following intravenous infusion of dl-carnitine.

The pharmacokinetics of l-carnitine were studied in adult male patients following intravenous infusion of dl-carnitine hydrochloride-L-Carnitine appears to distribute into a rapidly perfused and then a more slowly perfused body space following administration. The overall apparent distribution volume Vd (ss) is consistent with extracellular body water. Serum levels of l-carnitine, from two different dose levels were adequately described by a two-compartment model. 80% of the administered dose was recovered in 24 hour post dose urine.

Adult↗
PubMed1975

Androgen-dependent accumulation of carnitine by rat epididymis after injection of [3H]butyrobetaine in vivo.

After i.m. injection of [3H]butyrobetaine into rats, the accumulation of carnitine into the epididymis, prostate gland, seminal vesicles, testis and heart was studied. The concentration of radiolabeled carnitine into the cauda epididymis increased linearly with time up to 72 h after the injection of the precursor, while its level in the prostate and seminal vesicles decreased rapidly. Very low levels of carnitine were found in the testis. Castration reduced the carnitine accumulation by cauda epididymis to 6% of the control levels while treatment of castrated animals with testosterone propionate (500 mug/day) partly restored the carnitine uptake. Similar treatment with 17beta-oestradiol valerate or 17alpha-hydroxyprogesterone had no effect. Surprisingly, cyproterone acetate (5 mg/day) also significantly stimulated carnitine accumulation by the epididymis to a level above that of the castrated controls. Simultaneous injection of both cyproterone acetate and testosterone propionate to castrated animals caused an additive effect of these steroids. This indicated that cyproterone acetate in this system is working as a weak androgen. Treatment of rats with 17beta-oestradiol valerate also reduced carnitine accumulation by the cauda epididymis. This is due to suppression of pituiatry gonadotrophin secretion, since concommitant treatment with testosterone propionate (500 mug/day) caused a normalization of the carnitine uptake. Treatment of intact rats with cyproterone acetate significantly reduced the epididymal weight, but not the carnitine accumulation. 17alpha-Hydroxyprogesterone treatment had no effect either on the epididymal weight or the accumulation of the carnitine. Unilateral orchiectomy reduced the carnitine accumulation by the cauda epididymis to about 40% of that occurring in the non-operated control side. This indicates that the luminal contact between the testis and epididymis or the luminal content of the epididymis itself is of importance for the androgen-dependent metabolic process occurring in the cauda epididymis. Castration or hormone treatment did not change the conversion of butyrobetaine to carnitine, or the carnitine uptake by heart. Carnitine uptake by the testis after [3H]butyrobetaine injection was rather low and this would exclude the possibility of synthesis of carnitine in the testis as a source of epididymal carnitine. Carnitine only accumulated in the cauda epididymis in vivo 4 to 96 h after injection of [3H]butyrobetaine. The presence of radioactively labeled butyrobetaine or methylcholine was not detected.

Animals↗
PubMed1979

Uptake and esterification of circulating carnitine by aorta and heart in rabbits in vivo.

Disappearance of intravenously injected DL-[methyl-14C]carnitine from the bloodstream and its uptake and esterification by heart and aorta were studied in rabbits fed atherogenic or non-atherogenic control diets. The disappearance rate of [14C]carnitine from the bloodstream was approximately 2-fold greater in animals fed the control diet than in those fed the atherogenic diets. No evidence was found for carnitine esterification in the blood. Circulating [14C]carnitine was taken up and esterified in both the heart and aorta of all animals regardless of diet; however, on comparing dpm/mg lipid-free dry weight, uptake of [14C]carnitine and accumulation of [14C]carnitine esters by the heart was greater (6-fold and 12-fold, respectively) than by the aorta. Analysis of defined arterial segments indicated that aortas in animals fed the atherogenic diet contained greater [14C]carnitine activity (4- to 8-fold) and greater acetyl-[14C]carnitine activity (4-fold) when compared to aortas of control animals; uptake of plasma [14C]carnitine and accumulation of acyl-[14C]carnitine compounds by the heart was independent of diet. Butyryl-[14C]carnitine, although not detected in aortas from animals fed the non-atherogenic or atherogenic diet for only 7 weeks, was detected in aortas from animals fed the atherogenic diet 17 weeks. Butyryl-[14C]carnitine was detected in heart tissue regardless of the animals' dietary regime. The increased uptake of circulating [14C]carnitine and its accumulation as both free and esterfied carnitine in atherosclerotic aortas occurred before the development of extensive macroscopic atherosclerotic lesions; this response of the aorta to atherogenic stimuli was not a general tissue response in that the heart did not respond similarly. Since blood carnitine is found predominantly in the plasma fraction, it is likely that these results refect the uptake and metabolism of plasma carnitine in vivo.

Animals↗
PubMed1979

Muscle carnitine deficiency. Genetic heterogeneity.

Two types of lipid storage myopathy have been associated with decreased content of carnitine in muscle. In "muscle carnitine deficiency", carnitine concentration is normal in serum, but reduced in muscle. In "systemic carnitine deficiency", apparently due to imparied synthesis of carnitine in the liver, carnitine content is low in both serum and muscle. We studied a woman with a corticosteroid-responsive, probably autosomal recessive, lipid storage myopathy. Carnitine therapy was ineffective and carnitine failed to correct the impaired fatty acid oxidation in muscle homogenates, in contrast to a previous case. Carnitine transport into skeletal muscle was normal. These observations suggest that ll cases of "muscle carnitine deficiency are not the same.

Adult↗
PubMed1979

Familial carnitine deficiency. A fatal case and subclinical state in a sister.

A 15-year-old girl with a large accumulation of lipid in the muscle fibers, was suffering from systemic carnitine deficiency. She died in acidosis. The blood carnitine level was normal. At necropsy, carnitine levels were low in skeletal muscles and heart, whilst a normal level was found in the liver. Carnitine palmitoyltransferase II and palmitoyl-CoA synthetase activities were increased, whereas carnitine acetyltransferase, glycerol-3-phosphate dehydrogenase (FAD) and succinate dehydrogenase were decreased. Investigation of blood and skeletal muscle of the family members revealed marked abnormalities in a 7-year old sister who had only minor neurological symptoms. Histochemical investigation revealed abnormal accumulations of lipid between the myofibrils. Carnitine was decreased in her skeletal muscle and blood. Muscular carnitine palmitoyltransferase II and palmitoyl-CoA synthetase were again increased in activity while glycerol-3-phosphate dehydrogenase (FAD) was decreased. The activities of succinate dehydrogenase, carnitine palmitoyltransferase I and glycerol-3-phosphate dehydrogenase (NAD+) were normal. The unexpected normal carnitine level in blood and liver of the deceased patient was attributed to muscle wasting, which was confirmed by the very high blood level of creatine phosphokinase. This fatal case indicates that the fasting condition must be avoided in persons with carnitine deficiency. In crises, glucose supply is necessary since gluconeogenesis may be blocked.

Adenosine Triphosphatases↗
PubMed1978

[14C]palmitate uptake in isolated rat liver mitochondria: effects of fasting, diabetes mellitus, and inhibitors of carnitine acyltransferase.

The rapid association of Na-[16-(14)C]palmitate with isolated rat liver mitochondria was measured by an oil separation method. This association was time and temperature-dependent and was absolutely dependent on the presence of exogenous ATP and CoASH and partially dependent on exogenous carnitine. Carnitine dependence was enhanced at lower concentrations of [(14)C]palmitate. At 6.5 micro M [(14)C]palmitate (molar ratio of palmitate to albumin equal to 0.54), the rate of association was linear for 20 sec and was increased more than 100% in the presence of carnitine. Carnitine-dependent association was inhibited by 2-bromopalmitate, an inhibitor of carnitine acyltransferase I, but not by (+)-octanoylcarnitine, a presumed inhibitor of carnitine acyltransferase II. The association of [(14)C]palmitate with mitochondria was enhanced from 190 to 330% in mitochondria isolated from fasted animals and from 160 to 230% in mitochondria isolated from diabetic, ketotic animals as compared to control animals. The enhanced association with mitochondria from fasted animals was inhibited by 2-bromopalmitate. These studies demonstrate a method of evaluating fatty acid association with mitochondria which, because of its dependence on carnitine and carnitine acyltransferase I activity, most likely represents true uptake into mitochondria. Furthermore, these studies indicate that the carnitine-dependent uptake of fatty acids into mitochondria is enhanced in the two ketotic states evaluated and that the carnitine acyltransferase system may be a regulatory site in ketone body production.

Acyltransferases↗