Low number of neurosecretory vesicles in neuroblastoma impairs massive catecholamine release and prevents hypertension

INTRODUCTION

Neuroblastoma (NB) is a pediatric cancer of the developing sympathetic nervous system. It produces and releases metanephrines, which are used as biomarkers for diagnosis in plasma and urine. However, plasma catecholamine concentrations remain generally normal in children with NB. Thus, unlike pheochromocytoma and paraganglioma (PHEO/PGL), two other non-epithelial neuroendocrine tumors, hypertension is not part of the usual clinical picture of patients with NB. This suggests that the mode of production and secretion of catecholamines and metanephrines in NB is different from that in PHEO/PGL, but little is known about these discrepancies. Here we aim to provide a detailed comparison of the biosynthesis, metabolism and storage of catecholamines and metanephrines between patients with NB and PHEO.

METHOD

Catecholamines and metanephrines were quantified in NB and PHEO/PGL patients from plasma and tumor tissues by ultra-high pressure liquid chromatography tandem mass spectrometry. Electron microscopy was used to quantify neurosecretory vesicles within cells derived from PHEO tumor biopsies, NB-PDX and NB cell lines. Chromaffin markers were detected by qPCR, IHC and/or immunoblotting.

RESULTS

Plasma levels of metanephrines were comparable between NB and PHEO patients, while catecholamines were 3.5-fold lower in NB vs PHEO affected individuals. However, we observed that intratumoral concentrations of metanephrines and catecholamines measured in NB were several orders of magnitude lower than in PHEO. Cellular and molecular analyses revealed that NB cell lines, primary cells dissociated from human tumor biopsies as well as cells from patient-derived xenograft tumors (NB-PDX) stored a very low amount of intracellular catecholamines, and contained only rare neurosecretory vesicles relative to PHEO cells. In addition, primary NB expressed reduced levels of numerous chromaffin markers, as compared to PHEO/PGL, except catechol O-methyltransferase and monoamine oxidase A. Furthermore, functional assays through induction of chromaffin differentiation of the IMR32 NB cell line with Bt2cAMP led to an increase of neurosecretory vesicles able to secrete catecholamines after KCl or nicotine stimulation.

CONCLUSION

The low amount of neurosecretory vesicles in NB cytoplasm prevents catecholamine storage and lead to their rapid transformation by catechol O-methyltransferase into metanephrines that diffuse in blood. Hence, in contrast to PHEO/PGL, catecholamines are not secreted massively in the blood, which explains why systemic hypertension is not observed in most patients with NB.

Effect of Supplementation with Saccharomyces Boulardii on Academic Examination Performance and Related Stress in Healthy Medical Students: A Randomized, Double-Blind, Placebo-Controlled Trial

In recent years, bacterial probiotic dietary supplementation has emerged as a promising way to improve cognition and to alleviate stress and anxiety; however, yeast probiotics have not been tested. The aim of the present study was to determine whether 30-day supplementation with Saccharomyces boulardii enhances academic performance under stress and affects stress markers. The trial was retrospectively registered at clinicaltrials.gov (NCT03427515). Healthy medical students were randomized to supplement their diet with Saccharomyces boulardii CNCM I-1079 or placebo before sitting for an academic examination, which served as a model of stress. The grades of a final examination adjusted to subject knowledge tested in non-stressful conditions was used as a primary outcome measure. Psychometrically evaluated state anxiety, cortisol and metanephrine salivary levels, and pulse rate were tested at a non-stressful time point before the intervention as well as just before the stressor. Fifty enrolled participants (22.6 ± 1.4 years of age, 19 males) completed the trial in the Saccharomyces and placebo arms. Supplementation with Saccharomyces did not significantly modify examination performance or increase in state anxiety, salivary cortisol, and metanephrine. However, the intervention resulted in higher increase in pulse rate under stress as compared to placebo by 10.4 (95% CI 4.2–16.6) min⁻¹ (p = 0.0018), and the effect positively correlated with increase in salivary metanephrine (Pearson’s r = 0.35, 95% CI 0.09–0.58, p = 0.012). An intention-to-treat analysis was in line with the per-protocol one. In conclusion, supplementation with Saccharomyces boulardii CNCM I-1079 appears largely ineffective in improving academic performance under stress and in alleviating some stress markers, but it seems to increase pulse rate under stress, which may hypothetically reflect enhanced sympathoadrenal activity.

[Biological diagnosis of pheochromocytoma: is there an interest in urinary metanephrines measurement over 3 consecutive days?]

Pheochromocytoma and paraganglioma are neuroendocrine tumors characterized by a catecholamine production potential. The biochemical diagnosis for this type of tumor is carried out through the metanephrine titration on 24-hours urines. Some authors have suggested that the sensitivity of the test could be improved by sampling and analyzing urines 3 days in a row (cycle) versus a unique measurement but this method has never been fully evaluated. The goal of this study was to establish a comparison of diagnosis performances between urinary metanephrines measurement for 3 consecutive days, and metanephrines measurement on a unique 24-hour sample. Patients of Brest Regional University Hospital whose 3-consecutive day 24-hour urine samples had been analyzed from January 2011 to May 2017 were included in this study. The primary endpoint was the comparison of diagnostic performances of urinary metanephrine titration over a single day versus 3 consecutive days. Eighty-two patients for a total of 103 cycles among which 7 revealed a pheochromocytoma were analyzed. ROC curve analysis shows that the metanephrine cycle titration method is more efficient than the metanephrine single titration method (metanephrine: AUC=0.881 against 0.826 respectively; normetanephrine: AUC=0.946 against 0.901 respectively). Urinary titration over 3 days allows the diagnosis of 100% (7/7) of pheochromocytomas against 85.7% (6/7) for the the single urinary titration. In conclusion, metanephrine titration over 3 consecutive days of 24-hours urine samples shows a better sensitivity and better diagnosis performances for detecting pheochromocytoma and paraganglioma than the single titration method.

High specificity of spot urinary free metanephrines in diagnosis and prognosis of pheochromocytomas and paragangliomas by HPLC with electrochemical detection

BACKGROUND

The metanephrines (MNs) in plasma and urine were proposed as biomarkers for the diagnosis of pheochromocytomas and paragangliomas (PPGLs). However, plasma free MNs and 24h urinary fractionated MNs were not satisfactory enough in specificity for the diagnosis of PPGLs. Moreover, the collection of 24h urine was inconvenient. This work examined the diagnostic and prognostic efficiency of free MNs in spot urine for PPGLs.

METHODS

We measured free MNs concentration in spot urine and plasma of 28 PPGLs patients and 155 control subjects by HPLC with electrochemical detection. Postoperative free MNs levels in spot urine and plasma of 14 PPGLs patients were also determined. Creatinine (Cr) concentration was used for the correction of urine volume.

RESULTS

The specificity of spot urinary free MNs/Cr in the diagnosis of PPGLs was significantly higher than that of plasma free MNs [normetanephrine (NMN), 98.7% (95.4%-99.8%) vs 93.0% (87.4%-96.6%); metanephrine (MN), 93.6% (88.5%-96.9%) vs 84.5% (77.5%-90.0%)]. Meanwhile, the positive likelihood ratios for spot urinary free NMN/Cr and MN/Cr were 69.21 and 13.29, compared with 12.68 and 5.30 for plasma free NMN and MN, respectively. For the PPGLs patients underwent surgery, the plasma free MNs level appeared an abnormal elevation and yielded false-positive results for some patients. Our findings were validated in an independent cohort, resulting in the specificity of 100% for both urinary free NMN/Cr and MN/Cr, and 97.3% and 83.8% for plasma free NMN and MN, respectively.

CONCLUSIONS

Spot urinary free MNs/Cr, superior to plasma free MNs, presented a promising biomarker for the diagnosis and prognosis of PPGLs.

Accuracy of recommended sampling and assay methods for the determination of plasma-free and urinary fractionated metanephrines in the diagnosis of pheochromocytoma and paraganglioma: a systematic review

PURPOSE

To determine the accuracy of biochemical tests for the diagnosis of pheochromocytoma and paraganglioma.

METHODS

A search of the PubMed database was conducted for English-language articles published between October 1958 and December 2016 on the biochemical diagnosis of pheochromocytoma and paraganglioma using immunoassay methods or high-performance liquid chromatography with coulometric/electrochemical or tandem mass spectrometric detection for measurement of fractionated metanephrines in 24-h urine collections or plasma-free metanephrines obtained under seated or supine blood sampling conditions.

RESULTS

Application of the Standards for Reporting of Diagnostic Studies Accuracy Group criteria yielded 23 suitable articles. Summary receiver operating characteristic analysis revealed sensitivities/specificities of 94/93% and 91/93% for measurement of plasma-free metanephrines and urinary fractionated metanephrines using high-performance liquid chromatography or immunoassay methods, respectively. Partial areas under the curve were 0.947 vs. 0.911. Irrespective of the analytical method, sensitivity was significantly higher for supine compared with seated sampling, 95 vs. 89% (p < 0.02), while specificity was significantly higher for supine sampling compared with 24-h urine, 95 vs. 90% (p < 0.03). Partial areas under the curve were 0.942, 0.913, and 0.932 for supine sampling, seated sampling, and urine. Test accuracy increased linearly from 90 to 93% for 24-h urine at prevalence rates of 0.0-1.0, decreased linearly from 94 to 89% for seated sampling and was constant at 95% for supine conditions.

CONCLUSIONS

Current tests for the biochemical diagnosis of pheochromocytoma and paraganglioma show excellent diagnostic accuracy. Supine sampling conditions and measurement of plasma-free metanephrines using high-performance liquid chromatography with coulometric/electrochemical or tandem mass spectrometric detection provides the highest accuracy at all prevalence rates.

Monoamine oxidase A down-regulation contributes to high metanephrine concentration in pheochromocytoma

CONTEXT

The high diagnostic performance of plasma-free metanephrines (metanephrine and normetanephrine) (MN) for pheochromocytoma (PHEO) results from the tumoral expression of catechol-O-methyltransferase (COMT), the enzyme involved in O-methylation of catecholamines (CAT). Intriguingly, metanephrine, in contrast to epinephrine, is not remarkably secreted during a stress in hypertensive or normotensive subjects, whereas in PHEO patients CAT and MN are both raised to high levels. Because epinephrine and metanephrine are almost exclusively produced by the adrenal medulla, this suggests distinct CAT metabolism in chromaffin cells and pheochromocytes.

OBJECTIVE

The objective of the study was to compare CAT metabolism between adrenal medulla and PHEO tissue regarding related enzyme expression including monoamine oxidases (MAO) and COMT.

DESIGN

A multicenter comparative study was conducted.

STUDY PARTICIPANTS

The study included 21 patients with a histologically confirmed PHEO and eight adrenal glands as control.

MAIN OUTCOME MEASURES

CAT, dihydroxyphenol-glycol, 3,4-dihydroxyphenylacetic acid, and MN were measured in adrenal medulla and PHEO tissue. Western blot, quantitative RT-PCR and immunofluorescence studies for MAOA, MAOB, tyrosine hydroxylase, dopamine β-hydroxylase, L-amino acid decarboxylase, and COMT were applied on tissue homogenates and cell preparations.

RESULTS

At both the protein and mRNA levels, MAOA and COMT are detected less often in PHEO compared with adrenal medulla, conversely to tyrosine hydroxylase, L-amino acid decarboxylase, and dopamine β-hydroxylase, much more expressed in tumor tissue. MAOB protein is detected less often in tumor but not differently expressed at the mRNA level. Dihydroxyphenol-glycol is virtually absent from tumor, whereas MN, produced by COMT, rises to 4.6-fold compared with adrenal medulla tissue. MAOA down-regulation was observed in 100% of tumors studied, irrespectively of genetic alteration identified; on the other hand, MAOA was strongly expressed in all adrenal medulla collected independently of age, gender, or late sympathetic activation of the deceased donor.

CONCLUSION

High concentrations of MN in tumor do not only arise from CAT overproduction but also from low MAOA expression, resulting in higher substrate availability for COMT.

Pheochromocytoma as a catecholamine producing tumor: implications for clinical practice

Pheochromocytomas are catecholamine-producing tumors presenting with various clinical symptoms, but mostly with headache, sweating, palpitations and hypertension. If not properly diagnosed, secretion of catecholamines may lead to fatal cardiovascular consequences. Biochemical testing for pheochromocytoma should be performed not only in symptomatic subjects or in subjects with adrenal incidentaloma but also in subjects with a genetic predisposition for pheochromocytoma (multiple endocrine neoplasia type 2, Von Hippel-Lindau (VHL) syndrome, neurofibromatosis type 1 (NF 1)and mutations of succinate dehydrogenase (SDH) genes). Once a pheochromocytoma is proven, computed tomography (CT), magnetic resonance imaging (MRI) and functional imaging with [(123)I]-MIBG may be used for tumor localization. Adequate medical pre-treatment is essential for successful operation which is performed in most cases by laparoscopy. After tumor removal, further follow-up is necessary due to possible recurrence. Although prognosis after tumor resection is excellent, a significant proportion of pheochromocytomas recur, some as metastases. Thus, appropriate follow-up is mandatory.

The effect of temperature on the analysis of metanephrine for catechol-O-methyltransferase activity assay by HPLC with electrochemical detection

The enzyme catechol-O-methyltransferase (COMT) plays an important role in the metabolism of catechol estrogens and degradation of the catecholamine neurotransmitters, such as epinephrine. Several analytical methods, mainly high-performance liquid chromatography with electrochemical amperometric detection, have been reported for the analysis of catecholamines and their metabolites in biological fluids. In this paper we report the relevance of controlling temperature in calibration procedures of metanephrine, an O-methylated product of catechol-O-methyltransferase, using epinephrine as substrate. The results at higher temperatures show shorter retention times of metanephrine, no undue band-broadening and increased electro signals. This study also showed that, despite different temperatures leading to similarly specific activities of recombinant human COMT as expected, there are additional advantages in flow analytical methods where good sensitivity, efficiency and selectivity is required, mainly in tissues with low levels of COMT activity.

Biochemical diagnosis, localization and management of pheochromocytoma: focus on multiple endocrine neoplasia type 2 in relation to other hereditary syndromes and sporadic forms of the tumour

Approximately 50% of patients with multiple endocrine neoplasia (MEN) 2A or 2B develop pheochromocytoma. These tumours are almost exclusively benign and localized in the adrenal glands. About one-third are bilateral at initial diagnosis. Amongst patients with pheochromocytoma, those with MEN 2A have subtler symptoms compared to those with sporadic disease. Since pheochromocytomas in patients with MEN 2 often secrete catecholamines episodically (but metabolize them continuously to metanephrines), the first choice for biochemical diagnosis is the measurement of free metanephrines in plasma, with urinary fractionated metanephrines being the second choice. In patients with pheochromocytomas that produce exclusively normetanephrine, MEN 2 can be excluded. In patients with biochemically proven MEN 2-related pheochromocytoma, anatomical imaging of the adrenals (with either computerized tomography or magnetic resonance) should be obtained next. Functional imaging with specific ligands (e.g. scintigraphy with [(123)I]-metaiodobenzylguanidine or, if available, positron emission tomography with [(18)F]-fluorodopamine, [(18)F]-dihydroxyphenylalanine, [(11)C]-adrenaline or [(11)C]-hydroxyephedrine) may then be particularly useful in patients with distorted anatomy from previous surgery, in cases of equivocal biochemical data despite high clinical suspicion for a tumour, to rule out multifocal disease, or where there is suspicion of metastatic disease (e.g. tumours larger than 5 cm). Laparoscopic surgery is the treatment of choice and subtotal (cortical-sparing) adrenalectomy is the procedure of choice in bilateral pheochromocytomas.

An assay for determination of rat adrenal catechol-O-methyltransferase activity: comparison of spontaneously hypertensive rats and Wistar?Kyoto rats

A method has been developed for measurement of catechol-O-methyltransferase (COMT) activity in the rat adrenal gland. Epinephrine, synthesized in the adrenal gland, was used as substrate, and its enzymatic product, metanephrine, was quantified by high-performance liquid chromatography (HPLC) with fluorescence detection. The method has sufficient precision and accuracy. Soluble (S) and membrane-bound (MB) COMT activity in Wistar-Kyoto (WKY) rats was 20.7 +/- 3.5 and 18.6 +/- 3.4 pmol min(-1) mg(-1) protein (n = 5), respectively. To clarify the role of adrenal COMT in blood-pressure regulation, S and MB COMT activity in spontaneously hypertensive rats were determined. Respective activity was 18.6 +/- 3.4 and 17.0 +/- 1.1 pmol min(-1) mg(-1) (n = 5), which is similar to that in WKY rats. This finding suggests that COMT in the adrenal gland might not be related to blood pressure regulation.

Advances in metanephrine testing for the diagnosis of pheochromocytoma

Pheochromocytoma is a lethal tumor of chromaffin cells of the adrenal medulla that produces episodes of hypertension with the symptoms of palpitations, severe headaches, and sweating. The diagnosis of pheochromocytoma is a challenging one; autopsy series suggest that many pheochromocytomas are not clinically suspected, and the undiagnosed tumor can be associated with morbid consequences. The testing of catecholamines, metanephrines, and Vanillylymandelic acid commonly is used for screening of pheochromocytoma. The diagnostic value of various biochemical tests,as reported in recent Mayo and National Institutes of Health studies, have been compared and discussed in detail. The recent developments in the methodologies of metanephrines testing also are presented.

Microemulsion electrokinetic chromatographic analysis of some polar compounds

This study presents the optimization of a microemulsion electrokinetic chromatographic (MEEKC) electrolyte solution by using UV detection and with the method, simultaneous separations of chemically, biochemically and pharmaceutically related anionic and cationic compounds. Representatives of the compound groups were from isoflavonoids, benzodiazepines, metanephrines, diuretics and peptide hormones. The MEEKC separations under basic conditions were first optimized using a two-component isoflavonoid mixture as the sample and an electrolyte containing 10 mM tetraborate as the main buffer (pH 9.5). The stable microemulsion phase was adjusted with various amounts of octane, 1-butanol and sodium dodecyl sulfate (SDS). An only acidified electrolyte solution used in the study was made of phosphoric acid (pH 1.8) containing octane, SDS and ethyl acetate. The analyses with isoflavonoids showed that electrophoretic mobilities of the investigated compounds were highly related to the concentrations of SDS and 1-butanol with linear and parabolic correlation, respectively. However, addition of octane gave linear correlation only at low concentrations. In most cases four to six structurally related compounds and even 13 diuretics with various polar properties were separated from each other in basic microemulsion medium. The acidified MEEKC electrolyte gave good resolution for anionic metanephrines.

[The diagnosis of atypical pheochromocytoma: a challenge for the biologist as well]

Biological diagnosis of pheochromocytoma is relatively easy in those cases releasing great amounts of catecholamines with strong clinical features; instead, diagnosis could be more problematic in atypical or asymptomatic familial pheochromocytoma with small tumors secreting low catecholamine amounts. Several plasma and urine adrenergic markers must be used to confirm the clinical suspicion. We have discussed the biological data of three totally asymptomatic pheochromocytomas (cases no 2, 3, 4) and one case with a very discrete clinical manifestation (no 1). Three patients had very small tumors (4, 7 and 25 g) secreting preeminently adrenaline, one patient had a 45 g adrenal incidentaloma without clinical expression. Our study shows that, in these special cases, except for an inconstant increase of adrenaline, plasma and urine catecholamines and urine VMA can be normal. The most useful markers are plasma and urine methoxyamines. However, plasma methoxyamines are the most sensitive because their increase over reference values is by far greater than in urines. Several factors may explain these findings: a low tumoral secretion, the nature of the released amine, the short half-life of catecholamines in plasma and, in some cases, the involvement of intratumoral catecholamine metabolism. Analysis of the ratio NMN/MN in plasma provides an additional diagnosis tool to reveal adrenaline secretion abnormalities.

Adrenergic hyperactivity and metanephrine excess in the nucleus accumbens after prefrontocortical dopamine depletion

Selective dopamine depletion within the medial prefrontal cortex in rats is known to enhance dopamine and norepinephrine levels in the nucleus accumbens and to induce characteristic behavioral disturbances. The present study was designed to determine levels of adrenaline, apart from dopamine and norepinephrine, and metabolites in the nucleus accumbens after prefrontocortical dopamine depletion. Prefrontocortical dopamine depletion was carried out by injecting 6-hydroxydopamine, and it was validated through: the emergence of behavioral disturbances such as amphetamine-induced stereotypies, spontaneous motor hyperactivity, and enhanced "anxiety-like" responses and through postmortem quantification of catecholamine levels by using high-performance liquid chromatography. The findings indicated that lesioned rats exhibited more oral stereotypies after amphetamine, were hyperlocomotive, and showed more pronounced anxiety-like behaviors than controls. Following prefrontocortical dopamine depletion, postmortem concentrations of dopamine and norepinephrine, along with the metabolites 3,4-dihydroxyphenylacetic acid and vanillylmandelic acid, were reliably enhanced in the nucleus accumbens as expected, and dopamine turnover was decreased. Furthermore the nucleus accumbens contained higher levels of adrenaline and its transmethylated metabolite metanephrine. To sum up, prefrontocortical dopamine depletion induces motor and emotional disturbances in rats and alters the neurochemical profile of the nucleus accumbens, not only inducing dopaminergic and noradrenergic hyperactivity but also leading to adrenaline and metanephrine excess.

Plasma metanephrines are markers of pheochromocytoma produced by catechol-O-methyltransferase within tumors

This study examined whether the high sensitivity of plasma free metanephrines for diagnosis of pheochromocytoma may result from production of free metanephrines within tumors. Presence in pheochromocytomas of catechol-O-methyltransferase (COMT), the enzyme responsible for conversion of catecholamines to metanephrines, was confirmed by Western blot analysis, enzyme assay, and immunohistochemistry. Western blot analysis and enzyme assay indicated that membrane-bound and not soluble COMT was the predominant form of the enzyme in pheochromocytoma. Immunohistochemistry revealed colocalization of COMT in the same chromaffin cells where catecholamines are translocated into storage vesicles by the vesicular monoamine transporter. Levels of free metanephrines in pheochromocytoma over 10,000 times higher than plasma concentrations in the same patients before removal of tumors indicated production of metanephrines within tumors. Comparisons of the production of metanephrines in patients with pheochromocytoma with production from catecholamines released or infused into the circulation indicated that more than 93% of the consistently elevated levels of circulating free metanephrines in patients with pheochromocytoma are derived from metabolism before and not after release of catecholamines into the circulation. The data indicate that the elevated plasma levels of free metanephrines in patients with pheochromocytoma are derived from catecholamines produced and metabolized within tumors. Some tumors do not secrete catecholamines, but all appear to metabolize catecholamines to free metanephrines, thus explaining the better sensitivity of plasma free metanephrines over other tests for diagnosis of pheochromocytoma.

REPCAT: desktop expert system for interpreting and validating laboratory data for pheochromocytoma diagnosis with the database application Omnis 7

To aid in the validation and interpretive reporting of results from multianalyte diagnostic testing for pheochromocytoma (PHEO), we have developed a desktop personal computer-based laboratory expert system (REPCAT). REPCAT utilizes a commercial database application to run procedures that assess analytical and clinical data relating to patient urine or plasma samples. REPCAT was used to evaluate the raw data from >4000 24-h urine samples submitted to our laboratory for testing for the presence of PHEO. REPCAT performed equivalently to an expert pathologist in assessing the presence and class of PHEO (epinephrine, norepinephrine, or mixed secretor). No false negatives were generated and it assigned a correct interpretation (on the basis of subsequent clinical and biochemical investigation) for each of the primary diagnostic samples from these patients.

Stress mediators in the amniotic compartment in relation to the degree of fetal distress

In an attempt to locate biochemical markers specific for fetal distress we measured the amniotic concentrations of beta-endorphin, ACTH, cortisol, dopamine, norepinephrine and epinephrine with its major metabolite metanephrine (MN) in pregnancies with documented fetal well-being and pregnancies complicated by hypertension and fetal distress. While higher levels of cortisol and MN were found only in a selected subgroup of highly compromised subjects (p < 0.001 and p < 0.005, respectively), beta-endorphin increased significantly under conditions of moderate or severe intrauterine sufferance (p < 0.001 in both cases). Due to higher levels of the opioid even during the initial stage of fetal discomfort we evaluated its characteristics as a possible clinical marker. Specificity was 88.5%, whereas the sensitivity of 65.6% in the moderately compromised subgroup increased to 88.9% in severely suffering fetuses. Although more accurate and mainly real-time information on the fetal health status is obtained by means of biophysical methods, the determination of amniotic fluid beta-endorphin might be of clinical usefulness in prenatal diagnosis.

Pheochromocytoma presenting as exacerbation of post traumatic stress disorder symptomology

OBJECTIVE

The following case report and discussion is intended to increase awareness of the difficulties in diagnosing pheochromocytoma when a primary psychiatric diagnosis is first suspected.

METHOD

The case of a middle-aged combat veteran who was admitted with agitation and flashbacks is presented. Episodes of hypertension were initially believed to be related to agitation or alcohol withdrawal. When the hypertensive episodes persisted, further evaluation revealed a pheochromocytoma. In three years' follow-up since removal of the tumor, the patient has shown considerable improvement in the symptoms of Post Traumatic Stress Disorder (PTSD).

CONCLUSIONS

Pheochromocytoma should be considered in patients with psychiatric disorders if a pattern of hypertensive episodes persists or worsens. The case highlights the importance of medical evaluation in patients presenting with psychiatric complaints.

Malignant pheochromocytoma: effective treatment with a combination of cyclophosphamide, vincristine, and dacarbazine

STUDY OBJECTIVE

To determine the efficacy and toxicity of combination chemotherapy in patients with advanced, malignant pheochromocytoma.

DESIGN

Nonrandomized, single-arm trial.

SETTING

Governmental medical referral center.

PATIENTS

Fourteen patients with malignant pheochromocytoma confirmed by histologic tests. All patients had metastatic disease and elevated urinary catecholamine secretion.

INTERVENTIONS

After optimization of antihypertensive therapy, patients received cyclophosphamide, 750 mg/m2 body surface area on day 1; vincristine, 1.4 mg/m2 on day 1, and dacarbazine, 600 mg/m2 on days 1 and 2, every 21 days.

MEASUREMENTS AND MAIN RESULTS

Combination chemotherapy with cyclophosphamide, vincristine, and dacarbazine produced a complete and partial response rate of 57% (median duration, 21 months; range, 7 to more than 34). Complete and partial biochemical responses were seen in 79% of patients (median duration, more than 22 months; range, 6 to more than 35). All responding patients had objective improvement in performance status and blood pressure. Toxicity included expected hematologic, neurologic, and gastrointestinal effects of chemotherapy without serious sequelae. There were four minor hypotensive episodes and one minor hypertensive episode.

CONCLUSIONS

Combination chemotherapy with cyclophosphamide, vincristine, and dacarbazine is effective for advanced malignant pheochromocytoma. Urinary catecholamines are useful to ascertain biochemical response to therapy.

Radioimmunoassay of metanephrine and normetanephrine for diagnosis of pheochromocytoma

Sensitive and specific radioimmunoassays of metanephrine and normetanephrine were developed by use of 125I-labeled synephrine and specific metanephrine antibody, and 125I-labeled octopamine and specific normetanephrine antibody. Specific antibody for both metanephrine and normetanephrine was raised in rabbits by immunization with bovine serum albumin conjugated with the corresponding hapten, prepared by the method of Grota and Brown (Endocrinology 1976;98:615). The detection limits of the metanephrine and the normetanephrine radioimmunoassays were 2 and 6 pg/tube, respectively. Mean plasma metanephrine and normetanephrine values for 24 normal subjects were 62 (SD 14) and 100 (SD 40) ng/L, respectively. Mean urinary metanephrine and normetanephrine values for 22 normal subjects were 154 (SD 74) and 217 (SD 109) micrograms/day. For 14 pheochromocytoma patients, plasma metanephrine and normetanephrine values ranged from 29 to 683 and from 28 to 7850 ng/L, and urinary metanephrine and normetanephrine values were 606 to 6630 and 296 to 4800 micrograms/day, respectively. The present methods are simple and suitable for routine tests or for mass screening for pheochromocytoma.

Familial extra-adrenal pheochromocytoma. A new syndrome

Pheochromocytomas in the same anatomic site, the right renal hilum, occurred in a family over three successive generations. For two patients in the latter two generations, scintigraphy with iodine 131-tagged metaiodobenzylguanidine (MIBG) showed tumors only in the region of the right renal hilum, thus indicating that they were primary lesions. At surgery, except for lymph node metastases noted microscopically in one patient, tumors were found only near the right renal hilum. The adrenal glands seemed normal on inspection, palpation, and computed tomography. In another family, a mother and son had primary pheochromocytomas arising from the urinary bladder. We suggest that primary extra-adrenal pheochromocytoma is a syndrome in which specific genetic abnormalities determine sites of tumor development.

Derivatization and mass spectrometric behaviour of catecholamines and their 3-O-methylated metabolites

A method has been developed for the derivatization of both catecholamines (dopamine, noradrenaline and adrenaline) and their 3-O-methylated metabolites (3-methoxytyramine, normetanephrine and metanephrine) in a single run. The compounds were first incubated with methanolic hydrochloric acid to methylate those compounds that contain a benzylic hydroxyl group and were subsequently converted into their pentafluoropropionyl derivatives. The derivatives thus prepared, showed good gas chromatographic and electron-impact mass spectrometric properties and can be analysed in a single gas chromatographic run. The effect of the derivatization on exchange reactions in the aromatic ring was investigated because standard compounds with deuterium label in that part of the molecule are often used in isotope dilution measurements. The exchange of deuterium for hydrogen in the aromatic ring under derivatization conditions was found to be limited.

Radioenzymatic assay of catecholamines: real and apparent losses of labelled product

In the radioenzymatic assay of catecholamines, using catechol-O-methyltransferase, the yield of labelled product is frequently less than the expected value. This has been attributed by some workers to losses during the periodate oxidation of the O-methylated derivatives. Using spectrophotometric methods, we have demonstrated that there is no oxidative demethylation of the methoxycatecholamines during periodate oxidation. In a novel technique designed to determine the specific activity of small quantities of tritiated S-adenosylmethionine, high performance liquid chromatography with electrochemical detection was used to measure the amount of adrenaline formed from unlabelled noradrenaline, in the presence of phenylethanolamine-N-methyltransferase and tritiated S-adenosylmethionine. As well as the real losses occurring during solvent extraction and thin layer chromatography (demonstrated spectrophotometrically), apparent 'loss' of radiolabelled product may be due to the assumption that the value for the specific activity of the tritiated S-adenosylmethionine and the determination of the product's radioactivity are both absolutely accurate, with no allowance being made for the normal and expected experimental errors in such measurements.

[A simple and direct radioimmunoassay for serum and urinary metanephrine]

A simple, direct and specific radioimmunoassay for serum and urinary metanephrine was developed, in which we used 125I-Synephrine and specific antiserum generated in rabbits by injecting with metanephrine conjugated with bovine serum albumin as described by Grota and Brown. The sensitivity of the assay was 2 pg/tube. Intra- and inter-assay coefficients of variation were 2.6 approximately 7.8% and 5.0 approximately 9.6%, respectively. The recoveries of metanephrine added at two levels of 250 pg/ml and 500 pg/ml to ten serum samples and ten urine samples (hydrolyzed and diluted) were 96.7 and 108% in serum, and 94.8 and 103% in urine, respectively. Normal values of serum metanephrine were 40.3 +/- 25.8 pg/ml (mean +/- SD) from 20 normal subjects. Normal values of 24 hour urinary metanephrine excretion were 12.5 +/- 6.7 ug/day from 24 normal subjects. Serum metanephrine values for 7 patients with pheochromocytoma were 210 approximately 628 pg/ml. Urinary metanephrine values for 9 patients with pheochromocytoma 8.7 approximately 302 ug/day.

Reversed-phase ion-pair partion chromatography of biogenic catecholamines and their alpha-methyl homologues with tributylphosphate as stationary phase

Ion-pair partition chromatography is applied to the separation of the biogenic catecholamines and their alpha-methyl homologues. A useful selectivity has been obtained using an adduct-forming organic stationary phase (tributylphosphate). The retention of the compounds can be regulated easily by means of the concentration of the counter-ion (the perchlorate ion) in the mobile phase. The selectivity for separation of amines from amino acids can be influenced by changing the pH of the aqueous phase. The phase system shows a good long-term stability and reproducibility with respect to the capacity ratios and the efficiency.

Neuroendocrinoma of the jejunum: electron microscopic and biochemical analysis

A 56-year-old woman presented with a sudden, severe hemorrhage per rectum. Angiography localized a jejunal tumor, which was excised. Light microscopy suggested a neuroendocrine tumor, but neither a smooth muscle tumor nor a lymphoma could be excluded. Electron microscopy showed dense cored, single membrane bound secretory granules 150--220 nm in diameter; myofilaments were not observed. Biochemical analysis of tumor tissue yielded considerable amounts of catecholamines. VMA, 5-HIAA, and metanephrines. These combined ultrastructural and biochemical observations establish the diagnosis of neuroendocrine tumor; however, in this case neither type of information is sufficiently specific to define the tumor as either a paraganglioma or a carcinoid. Although paraganglia and mucosal endocrine cells in the GI are currently thought to constitute distinct cell types, they share numerous structural and functional properties, and they are both thought to be part of the APUD cell system. These parallels and similarities are shared by the neoplasms derived from them which often display features of both. In the absence of specific granule types or specific substances isolated from tumor tissue, only the application of specific immunocytochemistry techniques may allow the precise "functional" classification of such tumors.

Site of ocular hydrolysis of a prodrug, dipivefrin, and a comparison of its ocular metabolism with that of the parent compound, epinephrine

Dipivefrin is a prodrug of epinephrine which is hydrolyzed to epinephrine after absorption into the eye. The major site of this hydrolysis is shown to be the cornea. Some dipivefrin is absorbed unchanged into ocular tissues, but most appears as epinephrine and its metabolites within 15 min after topical application. Metanephrine is the major metabolite of epinephrine found in ocular tissues. It is found as soon as 15 min aftter application of either dipivefrin or epinephrine and appears in all the tissues tested. The data indicate that the peinephrine which is liberated by hydrolysis of topically applied dipivefrin is metabolized similarly to topically applied epinephrine. The monoamine oxidase metabolites of epinephrine appear 1 to 3 hr after treatment and are found mainly in the aqueous humor. After ocular application of either compound there appear to be uptake and storage of the exogenous epinephrine in the iris plus ciliary body. There is also some storage of unmetabolized epinephrine in the cornea.

Free metanephrine in human amniotic fluid as an index of fetal sympathetic nervous system maturation

Free metanephrine, a major metabolite of catecholamines, was measured in the amniotic fluid of 113 pregnant patients at various gestational ages. The results indicate that prior to 30 weeks the levels of free metanephrine are below the level of assay sensitivity. After 30 weeks' gestation there is a positive correlation of free metanephrine concentrations in amniotic fluid with gestational age. In addition there is a further increase in free metanephrine levels in amniotic fluid with labor.

Catecholamine metabolites in the aqueous of retinoblastoma

The aqueous humor of five patients with histologically proven retinoblastoma were analyzed for the main catabolic products of norephinephrine and epinephrine. In each case, there were no detectable levels of normethanephrine, metanephrine, vanilmandelic acid (VMA), and 3-methoxy, 4-hydroxy phenoglycol. The techniques are sensitive to 1 microgram/ml but will not detect the presence of homovanillic acid (HVA).

Malignant gastric neuroendogrinomas. Ultrastructural and biochemical characterization of their secretory activity

In two cases of malignant gastric tumors originally diagnosed as undifferentiated carcinomas electron microscopy revealed a neurosecretory type of granule. Subsequently tumor extracts were tested by biochemical methods and shown to have vanillylmandelic acid and 5-hydroxy-3-indoleacetic acid activity. Neither patient had signs or symptoms referable to the presence of these or related substances. These observations parallel those made in a variety of neuroendocrine tumors in which demonstration of neurosecretory granules or isolation of amine or peptide materials or their metabolites has not necessarily been reflected in clinical hormonal syndromes. Our findings indicate that regardless of clinically apparent hormonal activity or lack thereof, some undifferentiated gastric carcinomas may in fact derive from neuroendocrine APUD elements.

The use of sodium borate impregnated silica gel plates for the separation of 3-0-methyl catecholamines from their corresponding catecholamines

The use of sodium borate impregnated silica gel plates for the chromatographic separation of the catecholamines noradrenaline, adrenaline, and isoprenaline from their respective 3-0-methylated derivatives, normetanephrine, metanephrine, and methoxy-isoprenaline, is described. The parent catecholamines remain at the origin of the plates while the 3-0-methylated derivatives concentrate in discrete bands at the upper edge of the borate impregnated area (the "borate front").