Abstract
Plasminogen activator inhibitor (PAI-1) is induced in the vasculature and secreted into the vascular lumen in response to inflammation and oxidative stress. We have previously reported a fivefold increase in plasma PAI-1 from rats exposed to 708 kPa hyperbaric air. In the current study we assess the potential of human serum total PAI-1 as a biomarker for stress in compressed air diving. Eleven recreational divers, nine males and two females, completed four 2 h hyperbaric air exposures to 280 kPa in a pressure chamber over a period of 2 weeks. The air pressure corresponds to a diving depth of 18 m in water. Serum was collected before the study and again 3 h 30 min after completion of each hyperbaric exposure. All samples were taken in the afternoon to minimize the contribution of circadian variation. The analysis revealed no change in serum total PAI-1 after hyperbaric exposures within the group of divers (P = 0.064), but significant interindividual differences persisted throughout the study (P < 0.0005). A case of decompression sickness after the third round of hyperbaric exposure did not affect PAI-1. In conclusion, compressed air exposure to 280 kPa does not affect serum total PAI-1, and significant interindividual variation in PAI-1 levels may limit its usefulness as a biomarker. This does, however, not give a complete answer regarding PAI-1 in physiologically stressful dives. Further studies with different exposures and timing are needed for that.
Highlights
In compressed air diving, the diver breathes air at a density equal to that of the surrounding medium
Elevated oxygen pressure during submersion and nitrogen gas released as bubbles during decompression stress the circulatory system and may provoke a variety of symptoms collectively known as decompression sickness (DCS) (Vann et al 2011)
The incentive for examining PAI-1 as a stress biomarker in diving came from rat studies where hyperbaric air triggered a large increase in plasma PAI-1 independently of whether vascular bubbles were present after decompression (Eftedal et al 2012)
Summary
The diver breathes air at a density equal to that of the surrounding medium. We have previously reported that exposure to 708 kPa compressed air, corresponding to a water depth of 60 m, activates target genes for redox-sensitive transcription factors in the rat aorta (Eftedal et al 2012). These gene expression changes occurred independently of decompression-induced bubbles, as there were no differences between the responses of animals without a 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society
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