Aromatization of androgens by human abdominal and breast fat tissue

The ability of human abdominal, breast and axillary fat to convert androgens into estrogens was investigated by incubating labeled substrates in the presence of NADPH with a variety of cell preparations. The incubation products were subjected to phenolic partition, paper chromatography, methyl-ether formation, repeat chromatography and crystallization with cold carrier reference standards to constant specific activity. Androstenedione was converted to estrone and, to a lesser extent, to 17beta-estradiol by crude homogenates, minces, fat-free particulate fractions (1,000-100,000 time g) and isolated fat cells obtained from abdominal, breast or axillary fat. Testosterone was found to be aromatized as actively as androstenedione, but inthis case more 17 beta-estrodiol was formed than estrone. 19-Hydroxyandrostenedione-2 also served as substrate, givingresults similar to those obtained with androstenedione. Fat tissue obtained from cancerous breasts was found to be as active as normal breast fat (1-4 pg/g fat/90 min) and within the range found for abdominal fat (1-27 pg/g fat/90 min). In each case in which axillary fat was compared to breast fat from the same subject, the activity of the axillary fat was 5 to 10 times higher. The results indicate a possible role of adipose tissue as a significant extra-gonadal source of estrogens.