A simplified radio-enzymatic assay for total catecholamines in plasma

A simplified radio-enzymatic assay for total catecholamines in plasma

ABSTRACTS OF ANNUAL MEETING 1977 391 and thyroid hormone-free serum. After a 24-h incubation (4 CC). there is a further incubation with antirabbit g...

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ABSTRACTS OF ANNUAL MEETING 1977

391

and thyroid hormone-free serum. After a 24-h incubation (4 CC). there is a further incubation with antirabbit gamma globulin. Values found in normal subjects are 0.25±0.07(SD) nmoles/I (non-O.c. users) and 0.31 ±0.08 (O.c. users) respectively. It is useful to express results as T4/rT3 ratios. The mean ratio in normal subjects is 430. The T4/rT3 ratios in both thyrotoxicosis and myxoedema are decreased. Ratios are frequently decreased in acute and chronic non-thyroidal sicknesses where the assay has a potential application in elucidating the thyroid status. EVALUATION OF A RADIOMETRIC METHOD FOR THE DETERMINATION OF TOTAL AND UNSATURATED IRON BINDING CAPACITIES

A. N. & FRASER, c. G. Department of Clinical Biochemistry, Flinders Medical Centre, Bedford Park, South Australia The precise and accurate analysis of iron binding capacity still poses a number of problems. A commercial kit (RESO-MAT, Mallinckrodt Australia Pty Ltd) for the determination of total and unsaturated iron binding capacities based on the use of Fe 59 as a transferrin saturant has been evaluated and compared with a mechanized colorimetric method. The method was found to have acceptable precision and accuracy. The results obtained by the radiometric method compared well with those obtained using a colorimetric method. The radiometric test kit has a number of advantages over colorimetric methods in that haemolysis, lipaemia and icterus do not interfere, preparation of iron standards and calibration curves is not required, and minimal preparation and/or addition of reagents is necessary. HJOGE,

A SIMPLIFIED RADIO-ENZYMATIC ASSAY FOR TOTAL CATECHOLAMINES IN PLASMA

The Clinical Research Unit and Baker Medical Research Institute, A(fred Hospital, Prahran. Victoria SKEWS, HELEN & CARSON, VALERIE.

A two step radioenzymatic procedure for determining plasma catecholamines (noradrenaline plus adrenaline) has been developed. Catecholamines are isolated from 2 ml of plasma (pH 8.6) by adsorption on alumina and subsequent acid elution. Aliquots of the acid eluate are assayed for total catecholamines using 3H_S_ adenosylmethionine and catechol O-methyltransferase (COMT). 3H-normetanephrine formation is linearly related to noradrenaline concentration. Inhibition of COMT by plasma eluates necessitates internal standardization for each eluate. At plasma concentrations of 440 pg/ml the coefficient of variation is 4.3~~. The method has sufficient sensitivity and precision to measure total catecholamines in small amounts of plasma and tissues. A COMPUTER PROGRAMME FOR THE PROCESSING AND ANALYSIS OF BOTH RADIOIMMUNOASSAY (R.I.A.) AND ENZYMEIMMUNOASSAY (E.I.A.) DATA

J. Department of Chemical Pathology, Prince Henry's Hospital, Melbourne, Victoria The standard curve data are fitted to a second degree polynomial equation: Log [y) = a [log xj2 + b log x + c where x is concentration of standard y is the measured variable (counts or absorbance). The programme gives the coefficients to the line (a, b, c) and indication of 'closeness of fit'. Unknowns are calculated from this expression and the per cent error between duplicates is displayed. The application of this approach to the EMIli R ) assay of plasma diphenylhydantoin (Dilantin(R)), using a Centrifichem 400 is presented and shows extremely good correlation (r=0.991) between the computer results and those obtained graphically. Data are also presented on the precision of the EMIT Dilantin assay as performed on the Centrifichem and the correlation with results obtained by gas-liquid chromatography. CARR, S., QuTCH, K. & RussELL,

THE APPLICATION OF CURVE REGENERATION TO CONTINUOUS FLOW ANALYSIS

J. & FENELAN, A. Biochemistry Department, The Royal Melbourne Hospital, Parkville, Victoria Attempts to increase the rate of sampling in continuous flow analytical systems are limited by deviations from the ideal square wave concentration pattern which lead to imprecision and inaccuracy. The factors which determine such deviations include deformation of the concentration gradient both in the segmented stream and in the un segmented stream at the flow cell. Mathematical consideration has demonstrated that the problem of flow cell WARD, R.