Abstract
The relationship between maturation and response of the myocardium to ischemic injury remains controversial. Therefore, we studied isovolumic, buffer-perfused hearts(n=3-10/group) from 3 age groups of New Zealand white rabbits: 3 day(3d), 18 day (18d), and adult. Experiments (control (CON), 30 min no-flow ischemia(ISCH) and 30 min reflow(REF)) were performed at 37° C with performance measured as rate-pressure product (RPP). P31-NMR yielded ATP, creatine phosphate(CP), and inorganic phosphate(Pi) contents (μmol/gdw) and intracellular pH(pHi) at 4-6 min intervals. Na23-NMR with shift reagent (Dy(TTHA)3-) yielded intra-(Nai) and extracellular(Nao) sodium at 4 min intervals in 3d and 18d hearts.
During ISCH the rate of change in ATP, CP, Pi and pHi did not differ among groups. [ATP] differed among groups only at END-REF and was lower in adults (41 vs 65%CON for 3d and 18d). [CP] increased 4-fold with development. Recovery of CP and Pi (%CON) was lower in adult than 18d hearts. pHi was = 7.1 during CON and (161) REF and =6 at END-ISCH in each group. Nai reversibly increased = 2.5-fold during ISCH for both 3d and 18d hearts. Nao increased 120% in 18d vs 103% in 3d during REF. Recovery of RPP was best in 18d hearts and worst adult hearts.
Thus, tolerance to ischemia in the rabbit myocardium initially increases and then decreases during development. However, the results do not demonstrate a simple relationship between any metabolite or ion measured and developmental differences in functional recovery.
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Perry, S., Ingwall, J. ISCHEMIA IN THE DEVELOPING RABBIT MYOCARDIUM. Pediatr Res 21 (Suppl 4), 193 (1987). https://doi.org/10.1203/00006450-198704010-00159
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DOI: https://doi.org/10.1203/00006450-198704010-00159