Highly sensitive and rapid radioimmunoassay for aldosterone in plasma and cell culture medium.
A radioimmunoassay for aldosterone was developed using a sensitive and specific antibody and 125Iodinated-aldosterone. This assay could be used for direct determination of aldosterone in cell culture medium or after extraction of aldosterone from plasma by solid phase procedure using C18 Sep-pak cartridges. The very low cross-reactivity of the antibody with cortisol and corticosterone (0.005% and 0.04% respectively) would allow the direct determination of aldosterone in cell culture medium without any prior extraction step. Since the incubation is performed at room temperature for 1 h and then, at 4 degrees C for 15 min, the results can be obtained in less than 3 h. The assay was linear from 0.5 fmol/tube to 1500 fmol/tube with an ED50 at 30 fmol/tube. The accuracy of the assay estimated using spiked plasma samples with a known amount of aldosterone give a coefficient of correlation of 0.97 (n = 10) between the aldosterone concentrations found and expected levels. The within-assay variability for plasma aldosterone varied from 4.7 to 11.1% and the between-assay variability ranged from 13.9 to 14.2%. The coefficient of correlation between plasma aldosterone measured by this new assay or by a current assay was 0.8 (n = 43). In summary, the combination of a shortened incubation time with a simple solid phase extraction for aldosterone in serum samples represents the major advantage of the present assay over the current methodology which usually requires a chromatographic separation of the mineralocorticoid prior to radioimmunoassay. Therefore this assay would be useful in experimental studies as well as in clinical laboratory.
Molecular Pharmacology Laboratory, Clinical Research Institute of Montreal, Quebec, Canada.
M
M
Brochu
J
J
Féthière
M
M
Roy
H
H
Ong
A
A
De Léan
D000450:Aldosterone / Q000097:blood*; D000918:Antibody Specificity; D003429:Cross Reactions; D003470:Culture Media / Q000032:analysis; D006801:Humans; D007118:Immunoassay / Q000379:methods; D011863:Radioimmunoassay
D003470:Culture Media; D000450:Aldosterone