title: Cardioprotective effect of chronic hypoxia is blunted by concomitant hypercapnia.
abstract: The effect of chronic hypercapnia on cardioprotection induced by chronic hypoxia was investigated in adult male Wistar rats exposed to isobaric hypoxia (10 % O(2)) for three weeks. In the first experimental group, CO(2) 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 CO(2) levels in the inspired air suppress the development of the chronic hypoxia-induced cardioprotective mechanism, possibly by interacting with ROS signalling pathways.
authors.affiliation: Department of Developmental Cardiology, Institute of Physiology, Academy of Sciences of the Czech Republic, 142 20 Prague, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Neckár
authors.forename: O
authors.initials: O
authors.lastname: Sźárszoi
authors.forename: J
authors.initials: J
authors.lastname: Herget
authors.forename: B
authors.initials: B
authors.lastname: Ostádal
authors.forename: F
authors.initials: F
authors.lastname: Kolár
mesh_terms: D000818:Animals; D001794:Blood Pressure; D001835:Body Weight; D002908:Chronic Disease; D006339:Heart Rate; D006400:Hematocrit; D006935:Hypercapnia / Q000150:complications* / Q000503:physiopathology*; D000860:Hypoxia / Q000150:complications* / Q000503:physiopathology*; D008297:Male; D009203:Myocardial Infarction / Q000150:complications* / Q000503:physiopathology* / Q000517:prevention & control; D051381:Rats; D017208:Rats, Wistar