[Ammonia metabolism during perinatal period--ontogenesis of enzymes in pyrimidine biosynthesis and urea cycle system].
The enzymes and intermediate metabolite of pyrimidine biosynthesis and ammonia metabolism were studied during perinatal period in rats. The activity of carbamyl phosphate synthetase I(CPS I) in fetal rat liver was low up to the 19th day of gestation, but a rapid increase was observed on the 20th day of gestation. The activity of CPS I in adult liver was about three times as high as that on the 17th day of gestation in fetal rat liver. The activities of carbamyl phosphate synthetase II(CPS II) and aspartate transcarbamylase (ATC) in fetal rat liver were much higher than those in adult liver, but a rapid decrease was observed from the 17th day of gestation up to birth. The activities of CPS II and ATC in adult liver were about 5--10% of those on the 17th day of gestation. The change in orotate content during the perinatal period in fetal rat liver was parallel to changes in the activities of CPS I and ATC, and a rapid decrease in orotate content in the last gestational stage was related to a rapid decrease in CPS and ATC activities. These results indicate that the activities of CPS I and CPS II change from the end of the gestational stage up to birth, and the proposed metabolic regulation of fetal growth and developments of considerable interest.
D000375:Aging; D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001221:Aspartate Carbamoyltransferase / Q000032:analysis; D002222:Carbamoyl-Phosphate Synthase (Ammonia) / Q000032:analysis; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000032:analysis; D005260:Female; D005333:Fetus / Q000378:metabolism*; D008099:Liver / Q000201:enzymology; D009963:Orotic Acid / Q000032:analysis; D011247:Pregnancy; D011743:Pyrimidines / Q000096:biosynthesis*; D051381:Rats; D011919:Rats, Inbred Strains; D014508:Urea / Q000378:metabolism*
D011743:Pyrimidines; D009963:Orotic Acid; D000641:Ammonia; D014508:Urea; D001221:Aspartate Carbamoyltransferase; D002222:Carbamoyl-Phosphate Synthase (Ammonia); D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing)