Assessment of the Mineralocorticoid Activity of 18-Hydroxy-ll-deoxycorticosterone (18-OH-DOC) in the Isolated Toad Bladder

Abstract

1. The stimulatory effect of 18- hydroxy-11-deoxycorticosterone (18-OH-DOC) on active sodium transport was assessed by measuring the short-circuit current (sec) of the isolated urinary bladder of the toad. The sec pattern recorded with 18-OH-DOC administration was identical with that of other mineralocorticoids such as aldosterone, deoxycorticosterone (DOC) and 9α-fluorocortisol although the magnitude of response was not as great. 2. The affinity of 18-OH-DOC for the mineralocorticoid receptor of the toad bladder was estimated by its dissociation constant to be 1/7 that of either aldosterone or 9a-fluorocortisol and approximately equal to cortisol. 3. Substitutions at either the C-18 and/or C-21 position of the corticosteroid molecule can modify or eliminate stimulatory effect on active sodium transport. (Endocrinology89: 353, 1971)