| Popis: |
The activities of enzymes involved in adenine nucleotide metabolism and the concentration of their metabolic products were studied in the hearts of chickens from birth to advanced age. In particular, in order to investigate the main mechanisms which contribute to ensure availability of adenine nucleotides during ageing of the heart, IMP concentration and the activities of enzymes involved in its turnover were studied. In newborn animals, AMP degradation, though limited in amount, was found to lead to the final products of purine metabolism. In fact, the activity of hypoxanthine phosphoribosyl-transferase (HPRT)-the salvage enzyme of IMP-was not detected. On the contrary, in young chickens, the low concentration of final products of purine metabolism, together with a remarkable activity of HPRT and a high concentration of IMP, indicates that metabolic flux converges on the salvage pathway. In adult chickens, an increase of purine catabolism was observed. This, together with an optimal concentration of endogenous adenine nucleotides, is indicative of a particularly high AMP metabolism. Finally, in chickens of advanced age, a reduced purine catabolism appeared to take place, thus contributing to the maintenance of the adenine nucleotide pool. In ageing heart, a major role of IMP turnover probably consists in the preservation of adenine nucleotides and in the recovery of high-energy phosphates. |
