Effects of chronic hyperoxia on the cardiovascular responses to vasoactive compounds in the rabbit

This study evaluated the effect of hyperoxia on the pharmacokinetic function of the lung. Hyperoxia is known to disrupt the activities of the pulmonary prostaglandin dehydrogenase/reductase and angiotensin converting enzymes. This would be predicted to alter the activation/deactivation of prostaglandins or angiotensin. The ability of these enzyme systems to act upon these compounds was evaluated by measuring the changes in the peripheral vascular responses to exogenous prostaglandin and angiotensin. Two groups of conscious, chronically catheterized rabbits, one exposed to ambient air and the other to greater than 98% oxygen, were given bolus injections of angiotensin I, angiotensin II, prostaglandin E2, sodium nitroprusside, and phenylephrine before and during up to 88 h of air or oxygen exposure. The hyperoxic animals' responsiveness to angiotensin I and angiotensin II decreased by 47% and 55%, respectively, after 72 h of oxygen exposure. The hyperoxic animals demonstrated a 54% increase in the vasodilatory response to arterial prostaglandin E2. Normoxic rabbits demonstrated no changes in response to any of the compounds tested. These data indicate that chronic hyperoxia influences either the synthesis/degradation and/or vascular receptors to both angiotensin I and II and prostaglandins.