Longitudinal melatonin production in female laboratory rats during 1997-2006: possible modulatory effects of changing solar activity.

Earlier we reported that the urinary excretion of 6-sulfatoxymelatonin (aMT6s) displayed seasonal rhythms in laboratory rats and hypothesized that the horizontal intensity H of the geomagnetic field may act as seasonal zeitgeber. To test this, long-term experiments were performed with female Sprague-Dawley rats. In experiment I (n=12: 1997-1999) nocturnal aMT6s displayed a winter-summer increase by 30% and a rhythm with a phase-length of 24 months peaking in July 1998. In experiment II (n=12; 1999-2000) the winter-summer increase amounted to 40%. The estimated rhythm had a phase-length of 18 months with a peak in September 2000. Compared to experiment I both the rhythm-adjusted mean (MESOR, + 28%) and amplitude (+68%) were elevated. In experiment III (n=30; 2003-2004) the winter-summer increment was just 20%. A circannual rhythm with a peak in April/May was found. The MESOR was 13% higher than in experiment I but the amplitude was depleted ( -14%). In experiment IV (n=15; 2005-2006) a slight winter-summer increase (+15%) was found and a low-amplitude rhythm of 24 months phase-length peaking in June 2006. The MESOR was similar to experiment I but the amplitude was depressed (-36%). These results demonstrate that female rats within two years of age show elevated aMT6s during summer/spring which supports our initial hypothesis. The apparent inter-experimental amplitude variation indicates the involvement of additional variables. Based on our initial hypothesis, we postulate an involvement of the solar cycle affecting H leading to year to year variations and present supportive analyses.

Search for seasonal rhythmicity of pineal melatonin production in rats under constant laboratory conditions: spectral chronobiological analysis, and relation to solar and geomagnetic variables.

Earlier we reported that in a number of experiments pineal melatonin production in rats under constant laboratory conditions displayed seasonal rhythms but subsequently were not always able to confirm this. Since there was no indication under which conditions such rhythms may be present, we performed four consecutive identical experiments with untreated female Sprague-Dawley rats within the same animal room during 1997-2006. Nocturnal urine samples (19-23, 23-3, 3-7 h) were collected at monthly intervals over 494-658 d with 12 animals each in experiments I and II (1997-1999, 1999-2000), 30 animals in experiment III (2002-2004), and 15 in experiment IV (2005-2006). 6-Sulfatoxymelatonin (aMT6s) was measured by ELISA. The excreted aMT6s at each time interval as well as total nocturnal aMT6s-excretion (19-7 h) was submitted to standard statistical analyses as well as to a spectral chronobiological analysis to determine the period lengths of the components involved which was followed by processing with the single cosinor method. Seasonal rhythm components (circannual period length: 360 ± 60 d) were detected in experiment III (2002-2004) for the overall nocturnal excretion as well as for two sub-intervals (23-3 and 3-7 h) and in one night interval of experiment II (23-3 h). Multiple components with mostly short period lengths of around 100 d and some long ones of 500-650 d were found in the other experiments. Systematic MESOR and amplitude variations were observed during the experiments, being highest in experiment II (19-7 h, also 23-3 h and 3-7 h) and lowest in experiments I and IV. These results illustrate that seasonal melatonin rhythms are not a general phenomenon in female laboratory rats indicating an involvement of unknown environmental cues. As an extension of our earlier hypothesis regarding a seasonal Zeitgeber function of the horizontal intensity H of the geomagnetic field showing circannual variations, we assume further modulation by the 11-yrs' sunspot cycle which leads to geomagnetic disturbances and could facilitate seasonal aMT6s rhythmicity during specific years.

Detection of catecholamines and metanephrines by radio-immunoassay in canine plasma.

This study investigated the applicability of two human radio-immunoassays (RIA) to detect epinephrine (EPI), norepinephrine (NE), and their O-methylated metabolites metanephrine (MN) and normetanephrine (NMN) in canine plasma. The analysis yielded a positive correlation between metabolites and their respective parent compounds: EPI and MN (r=0.63), NE and NMN (r=0.47), as well as between parent compounds, EPI and NE (r=0.48), and between metabolites MN and NMN (r=0.71). Moreover, EPI (r=0.99) and NE (r=0.77) concentrations determined by RIA did correlate positively with high pressure liquid chromatography (HPLC). However, there was limited agreement between both methods. It was concluded that complete validation tests for accuracy, precision and agreement are needed before this RIA can be applied to quantify catecholamines, metanephrine, and normetanephrine in canine plasma. The assay may prove to be a potential alternative to HPLC or tandem mass spectrometry in the work-up of pheochromocytoma and the detection of overall sympathetic activity in dogs.

Multicenter study on the diagnostic value of a new RIA for the detection of free plasma metanephrines in the work-up for pheochromocytoma.

Available laboratory test methods for the detection of elevated concentrations of catecholamines and their metabolites in urine and/or plasma are not always sensitive enough for the detection of pheochromocytoma. High-quality immunoassays for these compounds appear to be as accurate as high-pressure liquid chromatography (HPLC) or gas chromatography/mass spectrometry (GC-MS). Therefore, the current project aims to establish a new sensitive radioimmunoassay (RIA) for the measurement of free metanephrines in the plasma of patients in the work-up for pheochromocytoma. We report first results of an ongoing multicenter clinico-chemical evaluation study in hypertensive patients and normotensive volunteers. After an overnight fast plasma samples were collected on ice in EDTA- and heparin-coated tubes after insertion of an indwelling venous line and resting in the supine (patients) or sitting position (normal volunteers) for 30 min. Plasma metanephrines were measured by a newly developed RIA from IBL, Hamburg, Germany. Good agreement of the assay with the tandem mass spectrometry (LC-MS/MS) method for normetanephrine (r2=0.975) and for metanephrine (r2=0.985) could be demonstrated. Both specimens, EDTA and heparin plasma, can be used with the same results. The RIA has a good precision of <15% in the normal range and of <10% in the elevated concentration range. Our preliminary data suggest a high validity of the newly developed RIA for measuring free metanephrine and normetanephrine in hypertensive subjects in both EDTA and heparin plasma. Further work is required to determine the accuracy of the test in larger patient populations and in patients with pheochromocytoma.

Normative data on the daily profile of urinary 6-sulfatoxymelatonin in healthy subjects between the ages of 20 and 84.

Although the hormone melatonin is a key factor for the proper functioning of the circadian timing system (CTS) and exogenous melatonin has been shown to be beneficial in cases of CTS disturbances, a deficit of melatonin has yet to be defined as a disorder. The aim of our study was to collect a normative data set on 24-h melatonin excretion in healthy human adults living in a natural environment. Urine samples were collected from 75 healthy subjects (45 women/30 men; mean age 47.2, SD 19.5, range 20-84) after five consecutive periods: 2300-0700, 0700-1100, 1100-1800, 1800-2300 and 2300-0700 h. 6-Sulfatoxymelatonin (aMT6s) concentrations were analyzed in duplicate by IBL (Hamburg) using a highly sensitive, competitive ELISA kit. Twenty-four hour-aMT6s total amount (rho=-0.68, p<0.001), aMT6s nighttime excretion (rho=-0.69, p<0.001), aMT6s morning excretion (rho=-0.66, p<0.001) and evening excretion (r=-0.26, p=0.023) were negatively associated with age, whereas daytime excretion (r=-0.17, p=0.15) was not. The intra-subject night-day ratio varied up to 10.5 (mean 6.0) in young subjects (aged 20-35) and up to 5.4 (mean 2.8) in older individuals (age>65). The total amount of 24 h-aMT6s (range 7.5-58 microg) as well as the amount of aMT6s excreted during the nighttime period (range 327-6.074 ng/h) varied as much as 20-fold between individuals. Our data show an age-related decline in melatonin excretion in healthy subjects living in a natural environment. The high inter-individual variability of excretion rates may explain why a normative data set is of no use in replacement strategies.

Pro-gastrin-releasing peptide (ProGRP) and neuron specific enolase (NSE) in therapy control of patients with small-cell lung cancer.

In small-cell lung cancer patients tumor markers were used for disease monitoring. The goal of this study was to identify diagnostic efficiency in the detection of tumor behavior in small-cell lung cancer patients by using a relatively new tumor marker, ProGRP, in comparison to the established marker NSE. 34 consecutive small-cell lung cancer (SCLC) patients were included in this prospective study. The changes of the blood levels of ProGRP and NSE were compared to the clinical evaluation. Clinical monitoring was evaluated according to the standard criteria of the WHO. 19 patients had remission, 8 stable disease and 7 tumor progression under therapy. NSE and ProGRP were measured in sera before and after treatment with polychemotherapy. After tumor remission the NSE but also the ProGRP levels decreased significantly under treatment (p=0.0001 resp. p=0.0180). As suspected, pre- and post-treatment marker concentrations did not differ significantly in patients with stable disease. In progressive small-cell lung cancer patients an increase of ProGRP and NSE was detectable. Overall, a decrease of NSE was seen in 18 (95%) of all responders, while an increase during progression could be detected in 6 (86%) of the patients. Because 6 patients in remission showed an increase in ProGRP concentrations, the corresponding data are 68% in responders and also 86% in progressive SCLC-patients. In conclusion, ProGRP was helpful as a diagnostic aid for therapy control in small-cell lung cancer patients. A long-term follow-up indicated that ProGRP can be used to monitor disease either with tumor regression under therapy as well as detection of subsequent progression. ProGRP could be well suited to complete thepresent diagnostic panel for lung cancer.

Diagnosis of pheochromocytoma.

The purpose of this article is to give an overview on recent advances in the diagnosis, localization by imaging and treatment of pheochromocytoma. Pheochromocytoma is a mostly benign tumor (malignancy rate 10-15%) which arises from chromaffin cells with excessive catecholamine production and secretion. Most tumors are localized in the adrenals but 15-18% of the lesions are found extraadrenally (paragangliomas). Pheochromocytoma is a rare form of secondary hypertension; it can also be found as a feature of familial disease (e.g. von Hippel-Lindau disease, MEN type II) due to genetic mutations of several genes that have been identified recently. In familial pheochromocytoma molecular genetic analysis has improved the diagnostic modalities. In such patients the tumor can occur bilaterally and patients often remain normotensive until the tumor produces sufficient catecholamines to have hemodynamic effects. The extreme importance of recognizing this tumor is evident from the fact that it can be successfully removed in about 90% of the cases, whereas if unrecognized the tumor poses great risk of death or devastating complications. Diagnostic screening includes measurement of catecholamines and their metabolites (metanephrines) in plasma and/or urine. Furthermore, pharmacological testing (e.g. clonidine suppression test) may be indicated in patients with moderately elevated catecholamines or when the diagnosis is still uncertain. Several imaging techniques are applied to localize the tumor. Abdominal CT scan is still considered the "gold standard" since about 98% of the tumors lie infradiaphragmatically. Magnetic resonance imaging (MRI) and MIBG-scanning are other useful methods. Recently, positron emission tomography (PET) based techniques have also been developed. After the diagnosis is made tumor removal following pharmacological pretreatment is the decisive therapeutic measure.

Simple, rapid and sensitive determination of epinephrine and norepinephrine in urine and plasma by non-competitive enzyme immunoassay, compared with HPLC method.

BACKGROUND: Measurement of the concentration of the free catecholamines epinephrine (adrenalin) and norepinephrine (noradrenalin) in humans is used for the diagnosis of pheochromocytoma and related diseases. METHODS: A non-competitive enzyme-linked immunosorbent assay (CatCombi ELISA) kit for the measurement of epinephrine and norepinephrine concentrations in plasma and urine was developed and validated. The assay procedure consists of sample extraction, chemical and enzymatic derivatization and immunological reaction steps. A sample volume of 10 microL urine or 300 microL EDTA plasma is required for duplicate determinations of both catecholamines. For method comparison we used a reversed phase HPLC by Chromsystems after extraction by aluminium oxide with electrochemical detection for the determination of epinephrine and norepinephrine. RESULTS: The CatCombi ELISA is accurate, sensitive, specific, and precise. Linear regression analysis of epinephrine and norepinephrine concentrations measured with the ELISA and with HPLC yielded highly significant correlations. CONCLUSIONS: The CatCombi ELISA kit as an alternative to HPLC methods is very useful for clinical applications as well as for basic research where a simple, rapid, accurate and reproducible assay for epinephrine and norepinephrine determinations is required.