Chemical structure and aldosterone receptor affinity of canrenoate-potassium metabolites in rabbits

Two new major metabolites of canrenoate-potassium (III) were isolated from rabbit livers, in addition to the known metabolite canrenone (II). One metabolite (MA) contains two additional oxygen atoms of unknown location. The second metabolite (MB), which was previously shown to interfere with a plasma aldosterone radioimmunoassay, is identified as 20-hydroxy canrenone. Canrenone (II) and metabolite MB showed significant affinity to rat kidney cytosol aldosterone receptors and might both contribute to the pharmacological effects of canrenoate-K (III).