THE METABOLISM OF STEROIDS BY TISSUE FROM NORMAL AND NEOPLASTIC RAT BREAST

Abstract

SUMMARY The metabolism of oestrone, dehydroepiandrosterone (DHA) and testosterone by normal mammary gland tissue from pregnant rats and by dimethylbenzanthracene (DMBA)-induced mammary tumours has been investigated. Oestradiol was the only compound regularly formed from oestrone. DHA was mainly converted to androst-5-ene-3β,17β-diol (Δ5-androstenediol), but another compound with the characteristics of an hydroxylated derivative of DHA was also formed. These tissues also had Δ4-5α-hydrogenase, 3-oxosteroid reductase and 17β-hydroxysteroid oxidoreductase activities when testosterone was used as substrate. Hormone-dependent and -independent tumours had higher enzyme activities towards oestrone and testosterone than had normal mammary tissue from pregnant rats. This difference cannot be accounted for solely by the difference in the cellularity of these tissues. The production of oestradiol by the hormone-dependent tumours was related to the growth rate of the tumour. No similar relationship was found for the metabolism of testosterone. Evidence is presented that hormone-independent tumours might be able to metabolize more oestrone than dependent tumours of similar growth rates.