7,12-DMBA-induced rat mammary tumour studied for hormonal responsiveness in vitro. 1. Short-term incubations of cell suspensions.

The effect of testosterone, progesterone, and 17-beta-oestradiol on the incorporation of tritiated thymidine into DNA was studied in vitro using cell suspensions from DMBA-induced rat mammary carcinomas and subcutaneous sarcomas. Both stimulatory and inhibitory effects of the hormones were seen. The two types of tumour reacted similarly. The validity of hormonal responsiveness in vitro compared with in vivo is discussed.