21-Hydroxypregna-1,4-diene-3,11,20-trione: a biliary metabolite of a cartilaginous fish, Raja sp

21-Hydroxypregna-1,4-diene-3,11,20-trione was isolated from skate bile and as an in vivo metabolite of 3H-1alpha-hydroxycorticosterone. Identity was established by chromatography and derivatization to constant 3H/14C ratio and mass spectrometry of the 20,21-acetonide. The new steroid was present in the free form and as the glucuronoside.