Cardioprotective Effect of Chronic Hypoxia is Blunted
by Concomitant Hypercapnia

J. NECKÁŘ^1,3, O. SZÁRSZOI^1,3, J. HERGET^2,3, B. OŠŤÁDAL^1,3, F. KOLÁŘ^1,3

Received March 20, 2002
Accepted June 6, 2002

Summary
The effect of chronic hypercapnia on cardioprotection induced by chronic hypoxia was investigated in adult male Wistar rats exposed to isobaric hypoxia (10 % O2) for three weeks. In the first experimental group, CO2 in the chamber was fully absorbed; in the second group, its level was increased to 4.1 %. Normoxic controls were kept in atmospheric air. Anesthetized open-chest animals were subjected to 20-min LAD coronary artery occlusion and 3-h reperfusion for infarct size determination (TTC staining). Chronic hypoxia alone reduced body weight and increased hematocrit; these effects were significantly attenuated by hypercapnia. The infarct size was reduced from 61.9 ± 2.2 % of the area at risk in the normoxic controls to 44.5±3.3 % in the hypoxic group (P<0.05). Hypercapnia blunted the infarct size-limiting effect of hypoxia (54.8±2.4 %; P<0.05). It is concluded that increased CO2 levels in the inspired air suppress the development of the chronic hypoxia-induced cardioprotective mechanism, possibly by interacting with ROS signalling pathways.

Key words
Rat heart • Chronic hypoxia • Hypercapnia • Infarction • Protection

Reprint requests
Dr. F. Kolář, Institute of Physiology, Academy of Sciences of the Czech Republic. Vídeňská 1083, 142 20 Prague , Czech Republic. Tel.: +420 24106 2559. Fax.: +420 2 4106 2125. E-mail address: kolar@biomed.cas.cz