J Steroid Biochem. 1982 Feb;16(2):157-63.  

Aromatization of 15 alpha and 16 alpha hydroxylated androgens in the human
placental using [1,2-3H]-substrates.

Cantineau R, Kremers P, De Graeve J, Gielen JE, Lambotte R.

This in vitro study reports data on the aromatization of [1,2-3H]-C19 steroids
in the human term placenta [androstenedione (III), testosterone (IV), 15
alpha-hydroxy-androstenedione (V), 15 alpha-hydroxy-testosterone (VI), 16
alpha-hydroxy-androstenedione (VII)]. The hydroxylated androgens were
microbiologically synthesized from commercially radiolabelled
[1,2-3H]-androstenedione and testosterone. Androstenedione and testosterone were
good substrates for the human placental aromatase (low Km values, high Vmax);
they strongly inhibited the 15 and 16 hydroxylated androgens aromatizations. On
the other hand, these hydroxylated compounds acted as poor substrates and were
only non-competitive inhibitors of the androstenedione and testosterone
aromatizations. However, 15 alpha-hydroxy-androstenedione could not be
disregarded as a potential precursor of 15 alpha-hydroxylated estrogens in the
human placenta.

PMID: 7078154 [PubMed - indexed for MEDLINE]