Pulmonary and Systemic Vascular Responses in Rats Exposed to Perinatal Hyperoxia
Greiner T, et al.
Premature infants used to die of lung immaturity. With surfactant treatment and ventilation, they have a much better survival rate. However, these interventions come with a cost. High oxygen causes retinopathy of prematurity which can lead to blindness. It may also have long-term effects on the cardiovascular system. In humans, teasing out the effects of the oxygen and the barotrauma (the pressure pushing the oxygen into the lungs) can be tricky.
The humble Sprague-Dawley rat is born at a stage of organ development similar to a premature infant. The lungs are saccular; the terminal ventilatory sacs have formed, but have not yet matured into alveoli. Exposing rat pups to high oxygen at birth can allow study of just the oxygen toxicity on the vascular function.
At birth, rats and mothers were housed in room air (21% oxygen) or 80% oxygen for two weeks. Three to six months later they were exposed to a hypoxic challenge (12% oxygen) and systemic and vascular responses were studied.
Hypoxia resulted in an increase in pulmonary vascular pressure; however, this observation was not primarily due to an increase in pulmonary resistance. Most was due to an increase in flow from an elevated stroke volume.
This model offers promise for understanding oxygen toxicity in the neonatal lung. Clinicians have assumed that barotrauma is responsible for much of the chronic lung and reactive airway disease seen in ex-premies. Challenging these rats with bronchoconstrictors could let us determine what role hyperoxia may play in these conditions.