Influence of steroid hormones on the incorporation of amino acids in uterine and cervical tissue of pregnant women.

The influence of steroids on protein synthesis in cervical and uterine tissue obtained from early and term pregnant women was studied by measuring the incorporation of labelled amino acids into total protein. It was found that oestradiol-17 beta and progesterone significantly reduced the incorporation of [3H]proline. Androstenedione and cortisol had no significant effect on the incorporation of [3H]proline even at high concentrations. The protein synthesis inhibitors puromycin and cycloheximide blocked the incorporation of [3H]proline to 80-85%. However, there was no further reduction in the incorporation in the presence of oestradiol. Oestradiol was found to reduce the incorporation of [14C]glycine but not that of [3H]serine. The results indicate that oestradiol and progesterone reduce protein synthesis in human cervical and uterine tissue and that this reduction, at least partially, involves collagen synthesis. Oestradiol and progesterone were equipotent under in vitro experimental conditions. The tissue concentration of progesterone in the pregnant uterus is, however, much higher than that of oestradiol. It seems therefore probable that progesterone rather than oestradiol restricts unopposed synthesis of proteins, presumably mainly collagen.