Effect of Actinomycin D and Puromycin upon Basal and LH‐Induced Steroidogenesis by Hamster Follicles in Culture

The role of protein synthesis in modulating steroid production by preovulatory hamster follicles (591–740 μm) was investigated in vitro using selective inhibitors of transcription (actinomycin D; 8 μg/ml) and translation (puromycin; 80 μg/ml). The results showed: (i) basal oestradiol production was increased in the presence of either actinomycin D or puromycin, suggesting the existence of a protein inhibitor of oestrogen synthesis; (ii) the initial stimulatory action of LH upon steroidogenesis is abolished by puromycin but not actinomycin D, suggesting that the synthesis of new protein is required but not new mRNA; and (iii) the preovulatory ovarian follicle grown in a defined culture medium is a good model system to study the hormonal regulation of gene expression.