A comparison of thein vivo uptake and metabolism of3H-oestrone and3H-oestradiol by normal breast and breast tumour tissues in post-menopausal women

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Abstract
After infusion of 3H-oestradiol or 3H-oestrone into post-menopausal women with breast cancer, there was a significant uptake of both steroids by breast tumour and normal tissue. The proportion of oestrogen present in tumour tissue as 3H-oestradiol after infusion of 3H-oestradiol (89.4 ± 3.5%, mean ± SD, n = 4) was significantly higher (p < 0.001) than in normal breast tissue (72.8 ± 3.3%) obtained from the same women. Similarly, after infusion of 3H-oestrone, the proportion of oestrogen present as 3H-oestradiol (48.4 ± 14.4%) was significantly higher than in normal breast tissue (19.1 ± 6.4%). These results suggest that conversion of oestrone to oestradiol is enhanced in breast tumour tissue with little metabolism of oestradiol. This would account for the higher concentrations of oestradiol reported in breast tumour tissue in the presence of increased oestradiol 17β-hydroxysteroid dehydrogenase activity.