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PubMedDate not supplied

Is epinephrine-induced platelet aggregation autoregulated by its metabolic degradation products in vivo?

BACKGROUND: Catecholamines play an important role in platelet activation and aggregation, epinephrine being the most potent one. Catecholamines are substantially increased during stress, exercise or smoking and could result in clinically important platelet activation if their action was not rapidly regulated. In the present study the possible fast regulation of epinephrine-induced platelet aggregation by its metabolic degradation products is investigated. MATERIALS AND METHODS: Human platelet rich plasma (hPRP) and washed rabbit platelets(wRP) were used for the study. The platelets irreversible aggregation induced by epinephrine and ADP were monitored by an aggregometer prior to and after the addition of the catecholamines degradation products metanephrine, 3-methoxy-4-hydroxy-phenyl-glycole-aldehyde (MHPGA),3-methoxy-4-hydroxy-phenyl-mandelic acid (VMA) 3,4-dihydroxy phenyl glycole (DHPG),3,4-Dihydroxy-phenyl-glycole-aldehyde (DHPGA) and the trimethoxy-phenyl-methyl-piperazine(TMP), a known free radical scavenger and calcium antagonist. Linoleic acid-lipoxygenase reaction, in vitro was monitored in the presence and absence of VMA. RESULTS: Metabolic degradation products possessing a methoxy group at position 3 of the phenolic ring markedly inhibited epinephrine and ADP-induced platelet aggregation at microM concentrations. The most potent inhibitor of both agonists was metahephrine, followed by MHPGA and VMA. TMZ also inhibited platelet aggregation at concentrations similar to VMA. Dihydroxy-phenyl compounds failed to induce any inhibition. None of the substances tested induced any aggregatory effect even at high concentrations (1 mM). VMA significantly inhibited linoleic acid-lipoxygenase reaction at 0.1 microM. CONCLUSIONS: Results indicate that catecholamines' degradation products possessing methoxy (-OCH3) groups can rapidly inhibit in vitro and ex vivo epinephrine-induced platelet aggregation. The inhibitory effects of methoxy phenolic derivatives on epinephrine-induced platelet aggregation may possibly be attributed to their free radical scavenging properties. There is substantial evidence to conclude that an internal rapid autoregulation of epinephrine-induced platelet aggregation, caused by its metabolic degradation products, takes place in vivo.

Animals↗
PubMed1998

Multiple endocrine neoplasia type IIa: a case report.

The authors reported a twelve year and four-month old girl who had prolonged fever for 2 weeks. Physical examination revealed a painless enlarged thyroid gland with firm consistency. Hyperparathyroidism was suspected because of hypercalcemia, hypophosphatemia, high level of serum alkaline phosphatase, and decreased density of long bones. Thyroid scan showed a cold nodule of the left upper lobe which subsequently proved to be a medullary thyroid carcinoma by high serum thyrocalcitonin level and pathological examination. Her 24-hour urinary vanillyl mandelic acid was in the normal range, and abdominal ultrasonography demonstrated normal adrenal glands. Multiple endocrine neoplasia type IIa (MEN IIa) was diagnosed by medullary thyroid carcinoma and hyperparathyroidism. However, the fully developed syndrome is characterized by the combined occurrence of medullary thyroid carcinoma, primary hyperparathyroidism, and pheochromocytomas. This syndrome is a rare, complex, and potentially lethal disease so early recognition and family screening are very important.

Carcinoma, Medullary↗
PubMed1976

[Catecholamine metabolism. Physiopathology and pathobiochemistry].

UNLABELLED: Metabolic studies on isolated rat organs showed that vanillyl mandelic acid (VMA) is dehydrogenated by liver homogenate and suspension of pseudomonas fluorescens. In the 100000 g supernatant fraction of homogenated rat kidneys enzymatic activity was sufficient for kinetic studies and the examination of substrate specificity, pH dependence and changes with age and sex of rats. Norepinephrine secretion and resorption may be influenced by antiarrhythmic drugs in vivo: after lidocaine, there was no change of the tyramine dependend norepinephrine depletion of rat hearts, Verapamil inhibited the uptake of norepinephrine by rat hearts. Immobilisation of the animals led to a significant decrease in the myocardial levels for norepinephrine and epinephrine, which was antagonised by recreation of 24 hours. Adumbran prevented the catecholamine depletion, so that the influence of the limbic system may be important for the mediation of sympathetic stimuli. CLINICAL STUDIES: Emotional stress was shown to lead to an elevated plasma level of norepinephrine, cortisole and free fatty acids. In patients undergoing surgery, the application of Valium and Fortral inhibited these stress reactions. After physical stress, which did not lead to significant changes of the catecholamine level in plasma of healthy volunteers, there was an elevated norepinephrine plasma level in patients with cardiac failure, which could be prevented by different antiarrhythmic drugs. The excretion of norepinephrine and VMA of these patients was also increased. It was shown, that sinus rate rose according to norepinephrine levels in plasma in this group, which was contrary to the behaviour of healthy volunteers, showing neither a norepinephrine overflow nor increased heart rate. In patients with atrial fibrillation, AV-conduction also increased with elevated norepinephrine levels in plasma. There was, however, no direct correlation. Determination of the cardiac AV-difference of plasma-norepinephrine levels showed a cardiac catecholamine overflow, which could be inhibited by specific and nonspecific antiarrhythmic drugs (Verapamil, Practolol). In studies of catecholamine and glucocorticoid metabolism, no significant difference of catecholamine and VMA could be determined in patients with normal blood pressure and arterial hypertension. There was, however, a tendency to increased values in patients of the last group. In postural hypotension, plasma levels and urinary excretion of catecholamines were decreased and showed no variation after physical stress in orthostasis and after nicotine. In patients with tumors of the adrenal cortex and medulla, a close relation of the disturbance in catecholamine and corticoid metabolism was revealed.

Animals↗
PubMed1998

[Idiopathic adrenal hemorrhage: a case report].

A 77-year-old man with a low grade fever persisting for 30 days consulted a local physician. A computed tomographic scan of the abdomen showed a mixed density mass on the left adrenal gland. He was referred to our hospital for further examination. Hormonal assay demonstrated a slightly high level of noradrenalin in the serum (18 pg/ml) and vanillyl mandelic acid in the urine (6.2 ng/ml). Magnetic resonance imaging revealed a heterogeneous mass lesion 3 cm in diameter with a high signal intensity on both T1 and T2 weighted images. Angiography showed a hypovascular mass in the supra-renal region suggesting an adrenal tumor or malignancy. Left adrenalectomy combined with en bloc nephrectomy was performed because of severe adhesion. Histologic evaluation showed hematoma without malignant cells due to idiopathic adrenal hemorrhage.

Adrenal Gland Diseases↗
PubMed1997

The evidence for conjugated mandelic and phenylglyoxylic acids in the urine of rats dosed with styrene.

Male Wistar rats were dosed intraperitoneally with styrene (400 mg/kg). Urine samples were collected over phosphate buffer, pH 6.5 for 24 h. Excretion of mandelic (MA) and phenylglyoxylic acid (PGA) amounted to 1.66 +/- 0.62 and 5.21 +/- 2.44% of dose, respectively, as determined by ion-pair HPLC. After acidic hydrolysis, the amount of MA and PGA found in urine increased to 2.10 +/- 0.84 and 6.81 +/- 3.20% (mean +/- S.D.; n = 7), respectively. A similar increase was observed after alkaline hydrolysis of urine samples. Differences between hydrolysed and non-hydrolysed samples were significant in the paired t-test (P < 0.05). Further, urine samples were fractionated by HPLC. Fractions were subjected to acidic hydrolysis and analysed by HPLC and GC/MS. Both MA and PGA were detected in the fraction which did not contain any of these metabolites before hydrolytic treatment. Thus, MA and PGA, which are used as biomarkers of exposure to styrene, form hydrolysable conjugates in the rat. At least a minor part of the total urinary MA and PGA is bound in these conjugates.

Animals↗
PubMed2000

Kinetic resolution of alpha-acetoxy carboxylic acids with homochiral SuperQuats.

Preliminary investigations focused on the kinetic resolution of (+/-)-alpha-acetoxy mandelic carboxylic acid chloride with isopropyl SuperQuat and isopropyl Evans' homochiral auxiliaries. The addition of 2 equiv. of the acid chloride to the lithium salts of the auxiliaries (SuperQuat and Evans') at -100 degrees C in the THF afforded the corresponding N-acyl auxiliaries in high chemical yields (95% and 89%) and d.e.'s of 66% and 40%, respectively. Using the same mandelic acid chloride but incorporating SuperQuat auxiliaries derived from (S)-phenylglycine and (S)-phenylalanine yielded the corresponding N-acyl SuperQuats in 86% and 90% and d.e. 's of 66% and 30%, respectively. Substituting the phenyl group within the alpha-acetoxy mandelic acid chloride for a n-butyl, tert-butyl and cyclohexyl group changed the d.e. significantly when kinetically resolved with isopropyl SuperQuat. The yields were all similar, i.e., approximately 90% but the d.e.'s varied considerably, with values of 20%, 50%, and 82%, respectively. Attempted kinetic resolution of alpha-methoxyphenylacetyl chloride using the lithium salt of isopropyl SuperQuat revealed a diasteroselectivity of 45%, significantly lower than that obtained with the corresponding alpha-acetoxy carboxylic acid chlorides.

Journal Article↗
PubMed1990

Urinary excretion of mandelic, phenylglyoxylic, and specific mercapturic acids in rats exposed repeatedly by inhalation to various concentrations of styrene vapors.

Adult male Sprague-Dawley rats were exposed by inhalation to various concentrations of styrene vapors (25, 50, 100, or 200 ppm) 6 h/day, 5 days/week, for 4 consecutive weeks. The concentrations were varied from day to day according to a random pattern allowing treated animals to be exposed five times to each concentration of styrene. Each day, the following urinary metabolites were analysed from samples collected during exposure (0-6 h) and after exposure (6-24 h): mandelic acid; phenylglyoxylic acid; and two mercapturic acids, N-acetyl-S-(1-phenyl-2-hydroxyethyl)-L-cysteine (M1) and N-acetyl-S-(2-phenyl-2-hydroxyethyl)-L-cysteine (M2). Various parameters of renal toxicity and hepatic microsomal and cytosolic enzyme activities were also measured. The results show that there is a very good relationship between the excretion of all four styrene metabolites and the degree of daily exposure to styrene over the entire period of urine collection, with correlation coefficients ranging from 0.82 to 0.98. The correlation was poor for mandelic acid during the 0-6 h period. There was no evidence that repeated exposure to styrene caused renal toxicity, nor induced hepatic microsomal enzyme activities; cytosolic glutathione S-transferase activity was increased moderately by 1.5 times. Thus, under conditions of exposure to styrene likely to be found in the workplace, all four metabolites measured were good indicators of styrene exposure throughout the length of the experiment. Since mercapturic acids result from the conjugation of styrene oxide with glutathione, the data suggest that measurement of these metabolites offers the possibility to monitor internal exposure to a toxic electrophilic compound more directly.

Acetylcysteine↗
PubMed1992

Simultaneous high-performance liquid chromatographic determination of urinary metabolites of benzene, nitrobenzene, toluene, xylene and styrene.

A high-performance liquid chromatographic method is described for the simultaneous determination of six urinary metabolites of several aromatic chemicals: phenol (from benzene), hippuric acid (from toluene), 3-methylhippuric acid (from xylene), mandelic and phenylglyoxylic acid (from styrene) and 4-nitrophenol (from nitrobenzene). Reversed-phase liquid chromatography was performed in an isocratic mode at 1 ml/min on a 5-microns C18 column using two mobile phases: (A) acetonitrile-1% phosphoric acid (10:90); (B) acetonitrile-1% phosphoric acid (30:70). Phase A separates the six metabolites well, but phase B allows to a more rapid and reproducible simultaneous determination of phenolic compounds than phase A. For these compounds a prior enzymic hydrolysis step using Helix pomatia juice is performed to hydrolyse their sulphate and glucuronate conjugates. The reproducibility and the specificity are both excellent. Furthermore, the method is rapid, economical and easily automated. The proposed method appears very suitable for the routine monitoring of workers exposed to these chemicals on the basis of the biological threshold limit values.

Benzene↗