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Assay methodology for plasma catecholamines and urinary metadrenalines.

Aziz, Abdul Abbas Abdul-Rassaul. (1978) Assay methodology for plasma catecholamines and urinary metadrenalines. Doctoral thesis, University of Surrey (United Kingdom)..

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A study of assay methodology for urinary metadrenalines and plasma catecholamines enabled some improvements to be suggested. For sample preparation in the assay of urinary metadrenalines, stearic acid-coated charcoal was introduced as a means of isolation. With optimized conditions of use for this coated charcoal, 75 +/- 5% (S.D.) of added 3H-metadrenaline and 74 +/- 5% (S.D.) of [3]H-normetadrenaline were recovered from urine. Following their isolation by coated charcoal, urinary metadrenalines were separated from each other by a cation exchanger (cellulose phosphate) and estimated fluorimetrically. The 24 h normal urine value obtained for metadrenaline (M) was 207 +/- 74 (S.D.) ug and for normetadrenaline (NM) it was 295 +/- 84 mug, which agrees well with values obtained by the reference method used, and with reported normal values for various published methods. A qualitative TLC method for urinary metadrenalines extracted by coated charcoal was developed. This could be clinically useful for detecting high levels of urinary metadrenalines. As an end-step, a reverse phase HPLC procedure has been used successfully for estimation of urinary metadrenalines, following HPLC trials which gave inadequate purification. After the isolation procedure using coated charcoal, the 24 h urinary values estimated by HPLC with UV detection, merely from two results, was 208 mug for NM and 107 mug for M. Using a Dowex-50 cation-exchange column for the sample preparation, the value for NM was 220 mug and for M was 74 mug. These values agreed with those obtained by the reference method used. However, when an electrochemical instead of a UV detector was used with the HPLC, only urinary NM could be estimated. Some pathological urines were assayed for their content of metadrenalines by means of HPLC combined with UV or electrochemical detection, or, for comparison, cellulose phosphate-fluorimetry. In the radioenzymatic assay method for plasma catecholamines an improvement was introduced that Involves the use of HPLC for separation of the [3]H-O-methylated derivatives of the plasma catecholamines which are formed by the enzymatic reaction. This improvement enables the single-isotopic method to match the precision of the double-isotopic method, since a correction for losses from the pre-HPLC step onward (although not during initial processing) was achievable by the UV detection of added unlabelled O-methylated compounds. Early results for plasma catecholamine values obtained by the present method were too high, due to the rather inefficient HPLC column used. With the more efficient column, in two assays the plasma noradrenaline was 155 pg/ml, adrenaline was 78 pg/ml and dopamine was 341 pg/ml. Pilot experiments with coated charcoal pointed to the possibility of using it as a sample preparation step in the analysis of certain drugs (exemplified by practolol and atenolol) from urine or blood.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Aziz, Abdul Abbas Abdul-Rassaul.
Date : 1978
Contributors :
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1978.
Depositing User : EPrints Services
Date Deposited : 22 Jun 2018 09:50
Last Modified : 06 Nov 2018 16:52

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