17 Beta-hydroxysteroid dehydrogenase and aromatase activity in breast fat from women with benign and malignant breast tumours.

The activity of 17 beta-hydroxysteroid dehydrogenase and aromatase was studied in adipose tissue taken from women aged between 22 and 83 years with benign or malignant breast lesions. The benign and malignant groups showed no significant differences in the mean activities of either of the enzymes studied. Under the experimental conditions used, the rate of conversion of oestrone to oestradiol varied markedly between subjects (6-169 ng oestradiol/mg protein/h), and there was a positive correlation between oestrone reduction and the total body weight of the tissue donor. In contrast, although the apparent Km for oestradiol (0.1-2.6 mumol/l) was lower than that for oestrone (9-14 mumol/l) the maximum velocity for oestrone production was very low (10-50 pmol/mg protein/h), and there was no obvious correlation with the age or body weight of the tissue donor. Aromatase activity in breast fat was at the lower end of the normal range of activity previously reported for abdominal adipose tissue, and there was no correlation between oestrone production and age or body weight.