Hypoxia is a common feature of many diseases of respiratory and cardiovascular origin (Aber & Bayley 1963). This is often accompanied by tissue damage and oedema formation. Circumstantial evidence has implicated the involvement of leukocytes (Mian & Marshall, 1993; Sanidas et al. 2001) and oxygen free radicals in the genesis of this cellular damage (Granger et al. 1989). The primary aim of this study was to determine the effects of whole body hypoxia on the production of oxygen free radicals in whole blood.
Sixty male Wistar rats (250-400g) were anaesthetised with a mixture of Hypnorm-Hypnovel 2.7 ml kg-1 and exposed to 3 min of spontaneously breathing either 6 % O2 (n = 15), 12 % O2 (n = 15) or 21 %O2 (n = 30), in a purpose built environmental chamber maintained at 38 °C. One millilitre of blood was extracted by cardiothoracic puncture from the left ventricle into heparinised vacutainer (final concentration of heparin 10 U ml-1). The rats were then humanely killed using Pentobarbitone at 0.8 ml kg-1, directly injected into the heart.
The chemiluminescent response of 10 ml blood was obtained by adding 90 ml isoluminol and 10 ml of buffered saline (pH 7.4) into flat bottomed, anti-reflective test tubes and following the chemilumunescent response every min for 10 min in a luminescence detector (LB 9509 Junior). The peak chemiluminescent response was noted in relative light units (RLU). Exposure of rats to 21 % O2 resulted in a basal level of chemiluminescence of 271 ± 12.3 RLU (mean ± S.D.). The intensity of this luminescence was significantly increased by exposure to 6 % O2 (695 ± 20.2 RLU)* and 12 % O2 (559 ± 16.7 RLU)*. (*P < 0.05, Student’s unpaired t test.)
This is the first reported study of an increase in the production of oxygen free radicals in blood, from animals exposed to whole body hypoxia. These findings have implications as to the role of oxygen free radicals in mediating cell damage during hypoxic episodes.
This research was supported by the Alexander S. Onassis Public Benefit Foundation.