A new model of oxidative stress in rat pups.

BACKGROUND

With current evidence, no specific oxygen concentration can yet be recommended in the resuscitation of the depressed term neonate.

OBJECTIVES

To design a neonatal rat model of resuscitation that mimics birth hypoxia and allows the study of the effects of resuscitation on outcome.

METHODS

Several key determinants were established utilizing P12 Sprague-Dawley rat pups. These include the ventilatory settings necessary to maintain normocarbic conditions and the amount and duration of hypoxia required to cause significant disruption of oxidative metabolism in the subjects' brains. Biochemical and cellular markers of oxidative injury were then compared in response to normoxic versus hyperoxic resuscitation.

RESULTS

Oxidative stress is produced in 12-day-old intubated rat pups with 15 min of 5% oxygen followed by 30 min of 100% oxygen or room air. Oxidized glutathione levels increased immediately after hypoxia and resuscitation then returned to control values at 24 h regardless of the resuscitate. Reduced glutathione levels were, however, significantly decreased 24 h after resuscitation with pure oxygen compared with the room air-resuscitated group (391 +/- 35 vs. 508 +/- 71 nmol/ml; p = 0.037). Stress from either resuscitate did not translate into evidence of oxidative modification detected by immunocytochemistry at 30 days.

CONCLUSIONS

We have demonstrated the ability to ventilate, create hypoxic stress, and resuscitate neonatal rats. While resuscitation with 21 or 100% oxygen results in a transient increase in oxidative glutathione levels, the oxygen-resuscitated group alone demonstrated a reduction in reduced glutathione 24 h later. Furthermore, these pups can then be returned to their dams for rearing, allowing ongoing evaluation of long-term effects of hypoxia and various modes of resuscitation.