Radioimmunoassay of free urinary 18-hydroxydeoxycorticosterone (18-OH-DOC) in patients with essential hypertension.

Specific antiserum was raised in white New Zealand rabbits using 18-hydroxydeoxycorticosterone-3-oxime-BSA complex as antigen. The urinary free 18-OH-DOC was estimated after dichloromethane extraction and separation in one paper chromatographic system (propylene glycol/toluene). The mean 18-OH-DOC excretion value (+/- S.D.) in normal subjects was 0.861 +/- 0.527 microgram/24 h (n=23). ACTH produced a 25-fold increase in the excretion of free 18-OH-DOC. Dexamethasone suppressed the values to the lower range of sensitivity. 32% of patients of essential hypertension showed a moderate increase in the free urinary 18-OH-DOC values. The mean value (+/- S.D.) in the low renin hypertension group was 2.50 +/- 1.49 microgram/24 h (n=19), in the normal renin patient group 1.84 +/- 1.22 microgram/24 h (n=38). The difference between controls and the hypertensive groups was statistically significant. Among the different hypertensive groups significant differences could not be calculated.