Effect of hyperbaric oxygen exposure on pulmonary clearance of 5-hydroxytryptamine

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Abstract
Clearance of 5-hydroxytryptamine (5-HT) by the lungs of normal and vitamin E-deficient rats was evaluated following a 60-min exposure to 100% O2 at 4 ATA [absolute atmosphere] (HBO). After exposure, lungs were isolated, ventilated, and perfused, with a recirculating system used for measurement of 5-HT clearance. Control lungs were obtained from rats exposed to air at 1 ATA. In control normal rats, fractional clearance of 5-HT was 0.78 .+-. 0.03 (mean .+-. SE). Following HBO 5-HT clearance was 0.55 .+-. 0.04 (P < 0.01). In control vitamin E-deficient rats, 5-HT clearance was 0.85 .+-. 0.05 and was decreased to 0.46 .+-. 0.03 (P < 0.001) following HBO. To evaluate the effect of recovery time after HBO on 5-HT clearance, separate groups of rats were killed at varying intervals post-HBO. In normal rats, 5-HT clearance had returned to control levels by 3-4 h after HBO; in vitamin E-deficient rats, clearance remained unchanged 4 h after HBO and was only 74% (P < 0.001) of control values 24 h post-HBO. Depression of pulmonary 5-HT clearance occurs in rat- due to hyperoxia and is potentiated by vitamin E deficiency. This represents a reversible alteration of lung function which requires vitamin E for complete recovery.