A non-chromatographic non-extraction radioimmunoassay for serum aldosterone

A direct radioimmunoassay for serum aldosterone was developed using a highly specific sntibody and 8-anilino-1-naphthalene sulfonic acid as a blocking agent to inhibit the binding of aldosterone to serum proteins. 125I-labeled aldosterone was used as the labeled antigen and polyethylene glycol was used to separate antibody-bound and free aldosterone. The minimum detectable concentration was 1.5 pg/tube. There were excellent correlations between the present method and other methods, i.e., 1) a method using tritiated aldosterone, 2) a method using dichloromethane extraction before assay, and 3) a commercial kit method. The intra-assay coefficient of variation was 6.9%, and the inter-assay coefficient of variation was 10.7%. The values found in normal human serum were comparable with those reported using other methods. The present radioimmunoassay eliminates both extraction of aldosterone from serum and chromatographic separation and requires only 0.1 ml of serum for assay.

[A simplified radioimmunoassay for serum aldosterone--non-extraction method with 125I-labeled aldosterone (author's transl)]

A simplified direct radioimmunoassay system for serum aldosterone measurement was developed by using radio iodine-labeled aldosterone and highly specific antiserum to aldosterone. 8-anilino-1-naphthalene sulfonic acid(ANS) was used to prevent the binding of aldosterone to serum proteins. Polyethylene glycol was used to separate the antibody-bound aldosterone from the free aldosterone as the precipitant. The minimum measurable concentration of aldosterone is 30pg/ml of serum by short incubation method (at 25 degrees C for 3hr incubation) and 15pg/ml of serum by long incubation method (at 4 degrees C for 20 hr incubation) respectively. Present radioimmunoassay eliminates extraction of the aldosterone from serum and chromatographic separation procedures, and requires only 0.1ml of serum sample for assay. The intra-assay precision was C. V. 6.9% (average of 4 samples) and the inter-assay precision was C. V. 10.7% (average of 4 samples). There is an excellent correlation between the extraction method and this direct method in serum aldosterone value obtained (correlation coefficient, 0.96). The normal value was 36.8+/-25.9pg/ml (recumbent) and 113.6+/-6.15pg/ml (upright).

F-antigen: nature, liver specificity, and release in experimental liver injury

F-antigen is a liver-specific antigen detected with antibody, raised in allogeneic (CBA) mice, to BALB/c mouse liver extract. The authors have confirmed the hepatic specificity of this antigen by showing it to be absent in extracts of extrahepatic organs of mouse and human origin. It is present in liver extracts of guinea pigs, rats, and rabbits, as well as in liver extracts from mouse and human sources. The antigen was present in the circulation of rabbits with acute carbon tetrachloride-induced hepatocellular injury. It was also demonstrated in the sera of 3 of 8 patients with acute hepatitis B antigen-positive hepatitis and in 1 of 4 patients with chronic active hepatitis. It was absent from the sera of 121 other patients with a variety of hepatic and nonhepatic diseases, and from the sera of 20 healthy subjects. The antigen is immunologically distinct from hepatitis B antigen, from the liver-specific lipoprotein antigen LP-2 of Meyer zum Buschenfeld, and from each of 15 individual human serum proteins tested.

Beta-glucuronidase of rat preputial gland. Crystallization, properties, carbohydrate composition, and subunits

Rat preputial gland beta-glucuronidase [ED 3.2.1.31] was purified by ammonium sulfate precipitation, ethanol fractionation, gel filtration on Sephadex G-200 and crystallization. The purified enzyme appeared homogeneous on electrophoresis in polyacrylamide gel, and on analytical ultracentrifugation and had a molecular weight of approximately 320,000, and a sedimentation coefficient of 12S. SDS polyacrylamide gel electrophoresis indicated that the enzyme consisted of subunits with molecular weight of 79,000, so the native enzyme appeared to be a tetramer. The Km with p-nitrophenyl beta-D-glucosiduronic acid as substrate was about 0.53 mM. The enzyme had a single pH optimum at 4.5. The enzyme had a very low content of sulphur-containing amino acid and contained 5.7 per cent carbohydrate, consisting of mannose, glucose, fucose, galactose, and glucosamine in a ratio of 44;9;6;2;41. Sialic acid was not detected in the crystallized enzyme.