title: Simple reproducible competitive radioligand assay for plasma protein binding of aldosterone.
abstract: A simple reliable and specific binding assay for the estimation of plasma (or serum) aldosterone-binding globulins (ABGs) is described. The method is based on the determination of the aldosterone-binding capacity of diluted plasma (with water 1:5), and relating it to the total aldosterone concentration in the same sample. The method distinguishes between the heat-labile and heat-stable ABG, the binding to the latter being determined following heating of plasma at 60 degrees C for 25 min. The binding to the heat-labile protein is determined by subtraction of the value for the binding to the heat-stable protein from the binding of the nonheated diluted plasma. Free aldosterone is separated from the bound fraction by adsorption of the former to dextran-coated charcoal. Two different concentrations of [3H]-aldosterone are used throughout the assay. Data obtained by incorporating chromatographic separation into the cross-reactivity procedure using several steroids are presented as evidence for the specificity of the method. This chromatography separates plasma ABG from corticosteroid-binding globulin. In 316 male or female controls, ABG capacity was 9.7 +/- 0.38% (SE)-range 2-17. Samples in females were taken during the first 8 days from the onset of menstruation. Higher ABG-binding capacity (p less than 0.001) was found during pregnancy.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000450:Aldosterone / Q000097:blood; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000097:blood* / Q000302:isolation & purification; D002648:Child; D002675:Child, Preschool; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011869:Radioligand Assay / Q000379:methods; D012016:Reference Values; D012712:Serum Globulins; D012737:Sex Factors; D014156:Transcortin / Q000302:isolation & purification
chemical_list: D002352:Carrier Proteins; D012712:Serum Globulins; D000450:Aldosterone; D014156:Transcortin