ESTROGEN AND PROGESTERONE CONTROL BASIC FIBROBLAST GROWTH-FACTOR MESSENGER-RNA IN THE RAT UTERUS

Cell proliferation and differentiation in the rodent uterus are probab ly controlled by the interaction of female sex steroids with polypepti de growth factors. Uterine basic fibroblast growth factor (bFGF) mRNA was measured by RNase protection during the time (days 2-4) of endomet rial cell proliferation in the pregnant rat. bFGF transcripts were det ected at each of the 3 days of pregnancy examined. To investigate the influence of oestrogen and progesterone on bFGF mRNA accumulation, ova riectomized rats were treated with oestradiol for 48 h followed by a s ingle injection of oestradiol, progesterone, the two steroids co-injec ted or oil vehicle alone. Uterine RNA was collected 6 h after the last hormone injection. Steroid treatments increased steady-state uterine bFGF mRNA compared with vehicle control animals as measured by RNase p rotection. Northern blot analysis of c-fos and c-jun mRNAs from these same treatment soups revealed increased protooncogene expression in th e uterus of hormone treated rats compared with the control animals. Te mporal analysis of bFGF mRNA in ovariectomized rats at 1, 3 and 6 h af ter acute oestrogen and oestrogen-progesterone co-administration showe d a dual pattern of transcript accumulation. Both hormone treatments i ncreased bFGF mRNA within 1 h compared with vehicle injected rats. Go- administration of the two hormones, however, repressed bFGF mRNA accum ulation relative to oestrogen at 3 and 6 h. Together, these studies pr ovide evidence that bFGF control of uterine cell proliferation in preg nant rats can occur from newly synthesized bFGF. Moreover, the results suggest that progesterone is a potent stimulator of bFGF expression i n the uterus.