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Updated: Aug 3, 2026

Modified Technique for the Use of Neonatal Murine Hearts in the Langendorff Preparation
Published on: March 4, 2022
pH paradox and neonatal heart
O Baron1, Y Saiki, I M Rebeyka
1Cardiovascular Research Group, 261 C Heritage Medical Research Center, Edmonton, Alberta, Canada.
Background:
To evaluate the functional status of the Na+/H+ exchanger in the neonatal heart.
Methods:
On the Langendorff system, isolated neonatal rabbit hearts were arrested by using cardioplegia with or without a specific Na+/H+ exchanger blocker, 5-(N,N dimethyl) amiloride (DMA) (20 microM). Ischemic period was 40 minutes at 37 degrees C or 120 minutes at 20 degrees C before 30 minutes of reperfusion at 37 degrees C. When DMA was added to the cardioplegia solution, it was also added to the reperfusate for the first 5 minutes of reperfusion (20 microM).
Results:
Postischemic developed pressure was 50.3+/-7.1 mmHg in the DMA group versus 25.9+/-6 mmHg in the control group (p<0.05) at 37 degrees C and 74.8+/-14.6 mmHg in the DMA group versus 60.6+/-11.5 mmHg in the control group (p<0.05) at 20 degrees C. Postischeimic diastolic pressure was 40.4+/-3.3 mmHg in the DMA group versus 28.4+/-7 mmHg in the control group (p<0.05) at 37 degrees C and 9.6+/-3.1 mmHg in the DMA group versus 15+/-3.7 in the control group (p<0.05) at 20 degrees C. Creatine kinase washout was 296+/-97 IU/L in the DMA group versus 1253+/-537 IU/L in the control group (p<0.05) at 37 degrees C and 370+/-156 IU/L in the DMA group versus 524+/-104 IU/L in the control group (p<0.05) at 20 degrees C.
Conclusions:
1) The Na+/H+ exchanger is active in the neonatal heart. 2) The Na+/H+ exchanger plays a key-role in the pathogenesis of reperfusion injury of the neonatal myocardium. 3) This exchanger is sensitive even for low H+ transmembrane gradients and even under hypothermic conditions.
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