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Urinary Metanephrines ELISA and RIA |
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Saturday, 24 June 2006 |
Background Information
Metanephrine (metadrenaline) and normetanephrine (normetadrenaline) are physiological breakdown products of the catecholamines adrenaline and noradrenaline, which play an important role as hormones and neurotransmitters. Metanephrine and normetanephrine are excreted in urine or broken down further in the body to the end product of catecholamine metabolism vanilylmandelic acid.
Catecholamines are biogenic amines which are synthesized from the amino acid tyrosine via the intermediate product dopa. Catecholamines are synthesized predominantly in the adrenal medulla and in the nerve ends of the sympthetic nerve system. Here they are stored in granula and released following a specific stimulus. The catecholamines exert their effects by binding to specific membrane receptors on the target cells. Afterwards, they are broken down rapidly by various enzymes. The main role of catecholamines is to help the body adapt to acute and chronic stress. Adrenaline affects mainly the heart muscles and metabolism, while noradrenaline acts as a vasoconstrictor on the peripheral arteries.
The diseases which are associated with an increased concentration of metanephrine and normetanephrine are catecholamine-producing tumors, for example, neuroblastoma, ganglioneuroma, and phaeochromocytoma. Of these, phaeochromocytoma has the greatest significance. Phaeochromocytomas are excessively catecholamine-secreting tumors, which originate in the adrenal medula and can, in combination with operative procedures and anaesthesia, lead to life-threatening situations. Around 10% of all phaeochromocytomas show malignant growth. In most cases, however, they can be cured by operative therapy combined with medication therapy using α-adrenergen antagonists. An unidentified phaeochromocytoma, on the other hand, poses a serious risk to the patient.
The determination of metanephrine and normetanephrine (or catecholamine) concentrations is therefore essential in patients with suspected phaeochromocytoma. These tests are also frequently used in the initial diagnosis of hypertonia.
RIA- The assay kit provides materials for the quantitative measurement of normetanephrine and metanephrine in urine. During the sample preparation normetanephrine and metanephrine are quantitatively acylated to their corresponding N-acyl-derivates. The assay procedure follows the basic principle of radioimmunoassays, involving competition between a radioactive and a non-radioactive antigen for a fixed number of antibody binding sites. The amount of 125I-labeled antigen bound to the antibody is inversely proportional to the analyte concentration of the sample. When the system is in equilibrium, the antibody bound radioactivity is precipitated with a second antibody in the presence of polyethylene glycol. The precipitate is counted in a gamma counter. Quantification of unknown samples is achieved by comparing their activity with a reference curve prepared with known standards.
ELISA- The competitive EIA kit uses the microtiter plate format. Metanephrine and normetanephrine, respectively, are bound to the solid phase of the microtiter plate. The acylated metanephrine and normetanephrine from the sample and solid phase bound nephrines compete for a fixed number of antiserum binding sites. When the system is in equilibrium, free antigen and free antigen-antiserum complexes are removed by washing. The antibody bound to the solid phase metanephrine and normetanephrine is detected by an anti-rabbit IgG-peroxidase conjugate using TMB as a substrate. The reaction is monitored at 450 nm with the amount of antibody bound to the solid phase nephrine being inversely proportional to the nephrine concentration of the sample.
ELISA vs. HPLC Comparison- Urine
The metanephrine and the normetanephrine concentrations in 27 urine samples were assessed using both the LDN EIA (x) and the HPLC method (y) (external QC samples from UK NEQAS). The UK control values are the mean of about 40 different HPLC users, and contain always one pathological sample per sending. The results of linear regression analysis showed the following correlation characteristics: y=0.88x - 0.10, r=0.99 for metanephrine and y=1.09x + 0.3, r=0.99 for normetanephrine.
Bottom Line: The LDN ELISA is comparable to the HPLC method
RIA vs. HPLC Comparison- Urine
The metanephrine and the normetanephrine concentrations in 21 urine samples were assessed using both the LDN RIA (x) and the HPLC method (y) (external QC samples from UK NEQAS). Therefore the correlation between RIA and HPLC is excellent. UK control values are the mean of about 40 different HPLC users, and contain always one pathological sample per sending. The results of linear regression analysis showed the following correlation characteristics for metanephrine: y=1.01x – 0.09, r=0.99, and for normetanephrine y=0.95x + 0.17, r=0.99
Bottom Line: The LDN RIA is comparable to the HPLC method
Available Kit Formats:Clinical Urinary RIA’s:
BA-0400 Normetanephrine RIA
BA-0500 Metanephrine RIA
BA-1300 Metanephrine/Normetanephrine RIA
Clinical Urinary ELISA’s:
BA-0400 Normetanephrine ELISA
BA-0500 Metanephrine ELISA
BA-1300 Metanephrine/Normetanephrine ELISA
Advantages of LDN Metanephrine Kits
• Customer Service! - We use the kits we sell, and we always offer a 24 hour turn around on almost all technical questions.
• Freedom from drug Interference!
• Complicated HPLC and LC/MS procedures can now be overcome with easy to use ELISA’s and RIA’s
• Excellent correlation with other methodologies.
• QUALITY- Produced according to ISO:13485
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