Regulation of 18-Hydroxydeoxycorticosterone in the Rat

Abstract

Simultaneous measurements of plasma 18-hydroxydeoxycorticosterone (18-OH-DOC), corticosterone and aldosterone were performed in the rat by using RIA [radioimmunoassay]. Under basal conditions, 18 OH-DOC levels averaged 11.3 .+-. 3.7 (SE) ng/ml. Plasma concentrations were increased 8-fold (86.8 .+-. 8.0 ng/ml) 1 h after 1 U [unit] s.c. ACTH. Dexamethasone suppressed 18 OH-DOC to less than 1.5 ng/ml, irrespective of Na+ intake. Neither Na+ depletion nor Na+ loading had any influence on 18 OH-DOC levels. Excellent correlation between 18 OH-DOC and corticosterone (r = 0.90, P < 0.001) was observed, whereas there was none between 18 OH-DOC and aldosterone (r = 0.061, P > 0.6). In the rat, 18 OH-DOC is an ACTH-dependent steroid which does not appear to be under the influence of the renin-angiotensin system.