Plasma xanthine oxidase activity correlates with the resistance to severe hypoxia in different species

A rapid polarographic method of measuring the O-form of xanthine oxidase (XOD) is described. Activities of this enzyme and oxypurine concentrations were measured in the plasma and cerebrospinal fluid (CSF) of 1, 12, 25 and 60-day-old rats. In the CSF, the highest oxypurine concentration was found in the group of 12-day-old rats (34.07 +/- 12.37 mumol.l-1), and it remained nearly at the same level in groups of older animals. Oxypurines in the plasma, on the contrary, are polarographically measurable on the first day of life; in groups of older rats their concentration is below the sensitivity of the method (5 mumol.l-1). This was explained by the development of XOD activity in the plasma, which increased from 8.17 +/- 2.80 to 99.46 +/- 13.85 nkat.l-1 during the first 60 days of postnatal life. The higher the normal plasma XOD activity, the shorter was the survival time of the species during interrupted hypobaric hypoxia. Adult guinea-pigs and hamsters have no measurable XOD activity in the plasma; adult rats and mice have 99.46 +/- 13.85 and 259.69 +/- 58.23 nkat.l-1, respectively. The survival time of these animals at 10,500 m was measured following exposure to an altitude of 8,000 m for 30 min and 15 minute normoxia. Guinea-pigs survived 100.8 +/- 13.84 min, hamsters 54.25 +/- 11.33, rats 25.2 +/- 5.37 and mice 3.33 +/- 1.00 min.