SCREENING RADIOIMMUNOASSAY FOR ALDOSTERONE IN PREHEATED PLASMA WITHOUT EXTRACTION AND CHROMATOGRAPHY

  • 1 January 1980
    • journal article
    • research article
    • Vol. 26  (1) , 41-45
Abstract
Plasma aldosterone was directly estimated radioimmunologically by using an antiserum raised against an aldosterone-3-oxime/bovine serum albumin conjugate, the estimation being on samples with and without heating (60.degree. C), and diluted and undiluted. Values obtained were compared with those by radioimmunoassay after extraction and chromatography. The correlation (even negative values were obtained) was poorest when the steroid was directly estimated in nonheated, undiluted plasma. Correlations were best (r = 0.918) for preheated and diluted native plasma, and the interassay coefficient of variation was 9.8% (n = 57). There were some extraordinarily high values. After equilibrium dialysis of native and preheated (60.degree. C) human plasma (15 plasma samples), the percentages of apparent free aldosterone and cortisol increased from 51.4 .+-. 2.6% (standard error of the mean) to 64.3 .+-. 1.6% and from 11.5 .+-. 2.2% to 61.1 .+-. 1%, respectively. Aldosterone-binding proteins apparently play a role in direct radioimmunoassays of aldosterone in plasma but by heating (with or without diluting) the plasma, direct assay can be used as a simple, fast and inexpensive screening method.