Tamoxifen-induced changes in the polyribosomes and associated mRNA of rat uterus

We have analysed the effect of tamoxifen on the accumulation of polysomes and their associated mRNA populations in the uterus of the immature rat. Tamoxifen caused the aggregation of ribosomes into polysomes but, when compared with the effects of oestrogen, the accumulation was delayed, of smaller magnitude and resulted in smaller polysomes. Tamoxifen did not inhibit oestrogen-induced polysome aggregation. Tamoxifen and monohydroxytamoxifen caused oestrogen-like changes in the polyadenylated mRNA population of uterine polysomes, but some quantitative and qualitative as well as kinetic differences were found in the response to the inhibitors when compared with the hormone. The reasons for these differences are discussed.