Lowered level of translatable messenger RNAs for carbamyl phosphate synthetase-I and ornithine transcarbamylase in the liver of tumor-bearing mice.
The activities of two urea cycle enzymes, carbamyl phosphate synthetase-I and ornithine transcarbamylase, in mouse liver gradually decreased after transplantation of Ehrlich tumor cells into the subepidermal tissue, and reached values of 60 and 65% of those of control mice, respectively, on the 21st day. The decrease in enzyme activities was attributable to decreased amounts of enzyme proteins as determined by radial immunodiffusion. Total hepatic RNA was translated in the presence of 35S-methionine in a cell-free system prepared from rabbit reticulocytes. The products were isolated by immunoprecipitation and sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Levels of translatable mRNAs for the two enzymes were measured in terms of the radioactivities incorporated into the enzyme polypeptides. The hepatic mRNA activities in the tumor-bearing mice were 35 and 35%, respectively, of those of control animals on the 7th day after the tumor transplantation, and 29 and 35%, respectively, on the 14th day. The results indicate that the decreases in amounts of the two urea cycle enzymes are substantially due to decreased levels of translatable mRNA.
D000818:Animals; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000378:metabolism*; D002286:Carcinoma, Ehrlich Tumor / Q000201:enzymology* / Q000378:metabolism; D008025:Ligases / Q000378:metabolism*; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D051379:Mice; D009954:Ornithine Carbamoyltransferase / Q000378:metabolism*; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*
D011506:Proteins; D012333:RNA, Messenger; D009954:Ornithine Carbamoyltransferase; D008025:Ligases; D002222:Carbamoyl-Phosphate Synthase (Ammonia)