Localization and synthesis of the tumor protein oncomodulin in extraembryonic tissues of the fetal rat.
The calcium-binding protein oncomodulin, previously found only in tumors, has been detected during rat development. Specific antisera to purified rat hepatoma oncomodulin (MW 11,500) were used to detect oncomodulin by radioimmunoassay (RIA) and by avidin-biotin-peroxidase complex (ABC) immunohistochemistry. Using RIA, oncomodulin was found to increase in placenta from below the limits of detection (2 ng/mg protein) on Day 13 to approximately 25 ng/mg on Day 16 of pregnancy, and to remain high through to the end of gestation. Determinations on separated inner and outer placenta showed the increase to be greater in the outer placenta (basal zone and decidua) than in the inner placenta (labyrinth). The ABC technique on paraffin sections produced positive staining for oncomodulin throughout the placenta, with the most intense staining occurring in the outer placenta (cytotrophoblast and giant cells of the basal zone). Parietal and visceral yolk sac, and amnion also stained positively, while fetal organs did not. Oncomodulin synthesis measured by [35S]methionine incorporation into immunoprecipitates occurred in isolated inner and outer placenta, whole placenta, the separated trophectoderm and endoderm of the parietal yolk sac, and amnion. No oncomodulin synthesis could be measured in visceral yolk sac, fetal liver, or 16-day embryo. This occurrence in developing and transformed tissues demonstrates that oncomodulin is an oncodevelopmental protein.
D000818:Animals; D002135:Calcium-Binding Proteins / Q000096:biosynthesis*; D005321:Extraembryonic Membranes / Q000378:metabolism*; D005260:Female; D006651:Histocytochemistry; D007106:Immune Sera; D007124:Immunoenzyme Techniques; D008715:Methionine / Q000378:metabolism; D008970:Molecular Weight; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution
D002135:Calcium-Binding Proteins; D007106:Immune Sera; C034733:oncomodulin; D008715:Methionine