TUMOR-GROWTH INFLUENCES SKELETAL-MUSCLE PROTEIN-TURNOVER IN THE PREGNANT RAT

The implantation of a fast growing tumor (the Yoshida AH-130 ascites h epatoma) to mid-pregnant rats resulted in no changes in fetus weight, in spite of an important body weight decrease observed in the mother. Tumor-bearing pregnant rats showed an accelerated muscle protein degra dation that resulted in decreases in both gastrocnemius and soleus mus cle weight and protein content. Although very slight changes were obse rved in liver protein turnover after tumor implantation, muscle protei n degradation and ubiquitin gene expression were increased (in relatio n with the non-tumor-bearing pregnant rats) in the first postimplantat ion period (0-4 d), whereas it remained lower in the second studied pe riod (4-7 d), compensating for the initial differences when the whole period (0-7 d) was considered, Similar results were observed when musc le protein synthesis was studied. On the whole, tumor growth resulted in a slightly decreased protein accumulation rate. The results present ed suggest that the implantation of this tumor in the pregnant rat has little or no consequences in fetal growth but results in an important muscle waste in the mother.