Embryonic versus adult myocardium: adenine nucleotide degradation during ischemia

Neonatal myocardium demonstrates better recovery from ischemia than does adult tissue. We tested the hypothesis that developmental differences in adenine nucleotide degradation might facilitate recovery by quantitating depletion of high-energy phosphates in nine-day-old embryonic (n = 9) and 15-month-old adult (n = 14) chicken hearts at 15-, 30-, 45-, and 60-minute intervals of normothermic ischemia in vitro. Nucleotides adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate and nucleosides adenosine, inosine, hypoxanthine, and xanthine were determined by high-performance liquid chromatography. Several observations in metabolite degradative response to ischemia were noted. The embryonic myocardium maintained higher adenosine triphosphate and adenosine monophosphate levels over the course of the investigation than did mature myocardium. Moreover, the adult group showed an increase in diffusible nucleoside pool metabolites. Relative immaturity of enzymes responsible for nucleotide degradation may facilitate postischemic recovery by preserving nondiffusible high-energy phosphate precursors to participate in salvage resynthesis of adenosine triphosphate.