The measurement of 18-hyroxy-11-deoxycorticosterone in human plasma by radioimmunoassay.
A radioimmunoassay method for the measurement of plasma levels of 18-hydroxy-11 -deoxycorticosterone (18 -OH-DOC) has been developed. The antiserum against 18-OH-DOC was produced in rabbits immunized against 18-OH-DOC-3-oxime-bovine serum albumin. Plasma (1-2 ml) was extracted with dichloromethane and chromatographed on paper. The purified extracts were incubated with antiserum at a 1/22,000 dilution for 1/2 hour at 37 degrees C and for 2 hours at 4 degrees C. Saturated ammonium sulfate was used to separate free from bound 18-OH-DOC. 1,2-3H-18-OH-DOC was added to all samples to correct for losses and to determine the percent free. Pyridine (0.1%) was added to solvents to maintain the stability of 18-OH-DOC. Recovery after extraction was 58 +- 8 (S.D)%. The accuracy and precision of the method were acceptable, and a sensitivity of 2 pg per sample enabled the measurement of very low levels of 18-OH-DOC. High specificity was demonstrated by a low blank value (0 +- 0.2 pg) and by demonstrating that alternative paper chromatography separation systems gave results not differing significantly from those obtained by the present method. The mean 8AM plasma 18-OH-DOC level was 8.5 +- 1.2 ng per 100 ml in18 normotensive control subjects. There was a marked response of plasma 18-OH-DOC to ACTH stimulation and dexamethasone suppression and a significant increase after 3 hours upright posture.
D015070:18-Hydroxydesoxycorticosterone / Q000097:blood* / Q000276:immunology; D000818:Animals; D000906:Antibodies / Q000032:analysis; D000918:Antibody Specificity; D002854:Chromatography, Paper; D003429:Cross Reactions; D003900:Desoxycorticosterone / Q000031:analogs & derivatives*; D005260:Female; D006801:Humans; D008297:Male; D008722:Methods; D011817:Rabbits / Q000276:immunology; D011863:Radioimmunoassay; D013997:Time Factors
D015070:18-Hydroxydesoxycorticosterone; D000906:Antibodies; D003900:Desoxycorticosterone