Chronic and intermittent hypoxia induce different degrees of myocardial tolerance to hypoxia-induced dysfunction

Giuseppina Milano, Antonio F. Corno, Silvio Lippa, Ludwig K. Von Segesser, Michele Samaja

Research output: Contribution to journalArticle

Abstract

Chronic hypoxia (CH) is believed to induce myocardial protection, but this is in contrast with clinical evidence. Here, we test the hypothesis that repeated brief reoxygenation episodes during prolonged CH improve myocardial tolerance to hypoxia-induced dysfunction. Male 5-week-old Sprague-Dawley rats (n= 7-9/group) were exposed for 2 weeks to CH (F1O2 = 0.10), intermittent hypoxia (IH, same as CH, but 1 hr/day exposure to room air), or normoxia (N, F1O2 = 0.21). Hearts were isolated, Langendorff perfused for 30 min with hypoxic medium (Krebs-Henseleit, PO2 = 67 mmHg), and exposed to hyperoxia (PO2= 670 mmHg). CH hearts displayed higher end-diastolic pressure, lower rate·pressure product, and higher vascular resistance than IH. During hypoxic perfusion, anaerobic mechanisms recruitment was similar in CH and IH hearts, but less than in N. Thus, despite differing only for 1 hr daily exposure to room air, CH and IH induced different responses in animal homeostasis, markers of oxidative stress, and myocardial tolerance to reoxygenation. We conclude that the protection in animals exposed to CH appears conferred by the hypoxic preconditioning due to the reoxygenation rather than by hypoxia per se.

Original languageEnglish
Pages (from-to)389-397
Number of pages9
JournalExperimental Biology and Medicine
Volume227
Issue number6
Publication statusPublished - Jun 2002

Keywords

  • Chronic hypoxia
  • Hypoxic preconditioning
  • Intermittent hypoxia
  • Isolated perfused heart
  • Reoxygenation

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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