MINERALOCORTICOID ANTAGONIST ACTIVITY OF AN 11-BETA 18-OXIDOPREGNANE

Removal of the 18-hydroxy group of the hemiacetal form of aldosterone transforms its activity from that of pure agonist to predominant antagonist. The 18-deoxy derivative possesses one third of the binding affinity of aldosterone for the cytoplasmic mineralocorticoid receptor of rat kidney and exhibits an approximate 2:1 antagonist to agonist ratio in both toad bladder and adrenalectomized rat bioassay systems. The promising properties of the 11β, l8-oxidopregnane tested included very low androgen receptor affinity and approximately equal effectiveness in vitro and in vivo in displacing aldosterone from mineralocorticoid-binding sites in the rat. © 1979 by The Endocrine Society.