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THE JOURNAL OF CARDIOVASCULAR SURGERY
Rivista di Chirurgia Cardiaca, Vascolare e Toracica
Indexed/Abstracted in: BIOSIS Previews, Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index Expanded (SciSearch), Scopus
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ORIGINAL ARTICLES CARDIAC SECTION
The Journal of Cardiovascular Surgery 2001 August;42(4):475-80
pH paradox and neonatal heart
Baron O., Saiki Y., Rebeyka I. M.
From the Cardiovascular Research Group 261 C Heritage Medical Research Center Edmonton, Alberta, Canada
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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) (20µM). Ischemic period was 40 minutes at 37°C or 120 minutes at 20°C before 30 minutes of reperfusion at 37°C. When DMA was added to the cardioplegia solution, it was also added to the reperfusate for the first 5 minutes of reperfusion (20 µM).
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°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°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°C and 9.6±3.1 mmHg in the DMA group versus 15±3.7 in the control group (p<0.05) at 20°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°C and 370±156 IU/L in the DMA group versus 524±104 IU/L in the control group (p<0.05) at 20°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.