Oestrogen-mediated gene expression is regulated at both the transcriptional and post-transcriptional levels. The molecular mechanism of transcriptional regulation has been well characterized. On the other hand, there is little understanding of the mechanism of post-transcriptional regulation. To clarify the mechanism of oestrogen-mediated post-transcriptional regulation, we focused on A+U-rich-element RNA-binding factor 1/heterogeneous nuclear ribonucleoprotein D (AUF1/hnRNP D), which is known as a regulator of cytosolic mRNA degradation and nuclear pre-mRNA maturation. However, little is known about the expression levels and the regulation of AUF1/hnRNP D mRNA in tissues. We further investigated the expression levels of AUF1/hnRNP D isoform mRNAs to determine whether AUF1/hnRNP D gene expression is regulated by oestrogen in the ovariectomized adult female rat uterus. Uterine AUF1/hnRNP D mRNA was induced by a single subcutaneous injection (1 microg/kg) of 17beta-oestradiol (E2), reaching a peak level within 6 h. Furthermore, we observed that the E2-induced AUF1/hnRNP D isoform mRNAs are p45 and p40 transcripts, and that E2-mediated induction is suppressed by the oestrogen receptor antagonist ICI 182,780. Finally, using the transcriptional inhibitor actinomycin D, we confirmed that the E2-mediated increase in AUF1/hnRNP D mRNA is caused by E2-dependent AUF1/hnRNP D mRNA stabilization.