[Incorporation of orotic acid in myocardial uridine nucleotides: effect of isoproterenol and ribose].
1. The efficiency of the terminal steps of de novo synthesis of pyrimidine nucleotides in the myocardium was investigated by means of labelled orotic acid. [5-3H] or [6-14C] orotic acid was injected intravenously into rats. One hour later, the animals were sacrificed and the radioactivity incorporated into uracil nucleotides was determined on the compounds separated by HPLC. 2. The results showed poor orotic acid conversion into cardiac uracil nucleotides. The observation that administration of ribose to rats increases the incorporation of the labelled precursor is consistent with the hypothesis that de novo synthesis might be limited by the availability of phosphoribosyl-pyrophosphate. 3. The treatment of animals by isoproterenol (5 mg . kg-1 body weight s.c.) 5 h prior to the injection of the tracer, which gave rise to an expansion of the uridine nucleotide pool, did not result in an increase in the incorporation of labelled orotic acid. 4. From these preliminary results it may be assumed that "salvage pathways" play a predominant role in the regulation of the level of uracil nucleotides in the heart.
D000818:Animals; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology*; D009206:Myocardium / Q000378:metabolism*; D009963:Orotic Acid / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012266:Ribose / Q000494:pharmacology*; D014500:Uracil Nucleotides / Q000378:metabolism*
D014500:Uracil Nucleotides; D009963:Orotic Acid; D012266:Ribose; D007545:Isoproterenol
Incorporation de l'acide orotique dans les nucléotides uridyliques du tissu myocardique : effet de l'isoprénaline et du ribose.