Abstract

PIP: Evidence for the presence of uteroglobin messenger RNA (mRNA) in the endometrium of pregnant rabbits and its translation in vitro in a cell-free system derived from wheat germ is presented. Total mRNA activity was measured by the incorporation of 3 5S-methionine into TCA-preceiptable peptides. Specific mRNA activity was measured by immunoprecipitation with specific uteroglobin antibodies purified by affinity chromatography. After dT-cellulose chromatography, 10% of the total mRNA activity was found in the bound fraction and 75% was found in the unbound fraction, which suggests that poly A sequences longer than about 20 residues are absent in most endometrial mRNA species. Tritiated-H-poly U hybridization did not reveal any poly A in the unbound fraction. However, 69% of the total mRNA activity was found in dT-bound RNA from rabbit liver. A single radioactive peak was given by the immunoprecipitable cell-free translation products of endometrial dT-RNA in 15% polyacrylamide gels containing sodium dodecyl sulfate. The addition of nonradioactive uteroglobin to the immunoprecipitation reaction completely displaced this peak, and was abolished in products of translation without additional endometrial RNA. The amount of uteroglobin mRNA in endometrial dT-bound RNA peaked on Day 4 of pregnancy and declined to nonpregnant levels on Day 8. This pattern paralleled that of uteroglobin secretion.