The activity of estradiol-17β-OH-dehydrogenase was determined in human breast tissues and compared in various pathological conditions. The major metabolite of estradiol-17β in human breast tissue was found to be estrone.
By cell fraction experiment the enzymatic activity was observed mainly in the particle fraction. The enzyme required DPN or TPN as cofactor, TPN giving higher activity than an equimolar amount of DPN. The optimal pH for the enzymatic oxidation of estradiol to estrone is 9. The various metal ions at a concentration of 1 ×10-3 M produced the inhibition of the enzymatic activity.
It was shown that there was no quantitative difference in the enzymatic activity of various pathological conditions, including mastopathy, fibroadenoma, breast cancer and normal breast tissue. The mean values of produtcion rate of estrone was slightly higher in fibroadenoma than in others but markedly higher in breast cancer than in others in same ages. Among fibroadenoma tissues from younger ages showed higher enzymatic activity than that from older ages, but such age-dependent difference was not found in other pathological tissues.
The comparison between histological findings and the enzymatic activity of breast cancer showed that acirrhous carcinoma had lower production of estrone than adenocarcinoma papilotubulare and medullary carcinoma.