SYNTHESIS AND REGULATION OF LEUKEMIA INHIBITORY FACTOR IN CULTURED BOVINE OVIDUCT CELLS BY HORMONES

Leukaemia inhibitory factor (LIF) is an essential factor for embryo im plantation. Factors generated by the oviduct cells (epithelial cells a nd fibroblasts) create the microenvironment for fertilization and firs t embryo stage development. Hence, it is feasible that the oviduct cel ls also synthesize LIF to promote and condition the embryo for implant ation in the uterus. In the present study, we investigated whether cul tured bovine oviduct epithelial cells and fibroblasts synthesize LIF. LIF production was measured in the conditioned medium of oviduct epith elial cells and fibroblasts, using LIF enzyme-linked immunosorbent ass ay. Moreover, expression of LIF mRNA was confirmed by LIF reverse tran scriptase-polymerase chain reaction in extracts of RNA from oviduct ep ithelial/fibroblast cells. Quantitatively similar amounts of LIF were detected in the culture medium of epithelial cells and fibroblasts. In cells cultured for 1-7 days, the levels of LIF in the medium increase d in a time-dependent manner. As compared to untreated cells, treatmen t of cells with 17 beta-oestradiol (1-100 ng/ml), but not progesterone (1-100 ng/ml) and insulin (20 ng/ml), increased the levels of LIF in a concentration-dependent manner (P < 0.05). Similarly, tumour necrosi s factor-alpha (100 ng/ml) significantly induced the levels of LIF. Th e effects of 17 beta-oestradiol (50 ng/ml) on LIF synthesis were enhan ced and not blocked in the presence of tamoxifen (1 mu g/ml), an oestr ogen receptor antagonist, suggesting that the stimulatory effects of 1 7 beta-oestradiol on LIF synthesis are not receptor-mediated. In concl usion 17 beta-oestradiol, but not progesterone, induces LIF synthesis by bovine oviduct epithelial cells and fibroblasts and this may play a n important role in the biology of early embryo development. However, the exact pathophysiological role of LIF within the oviduct needs to b e further investigated.