Differential influence of vitamin C on the peripheral and cerebral circulation after diving and exposure to hyperoxia

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology Vol. 315; no. 4; pp. R759 - R767
• Main Authors: Barak, Otto F, Caljkusic, Kresimir, Hoiland, Ryan L, Ainslie, Philip N, Thom, Stephen R, Yang, Ming, Jovanov, Pavle, Dujic, Zeljko
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.10.2018
• Subjects: Antioxidants; Ascorbic acid; Blood vessels; Brain; Cerebral blood flow; Dietary supplements; Diving; Doppler effect; Endothelium; Exposure; Hyperoxia; Ingestion; Oxygen breathing; Pressure; Respiration; Scuba diving; Seawater; Surfacing; Ultrasonic testing; Ultrasound; Vitamin C; cerebral blood flow; flow-mediated dilation; transcranial Doppler ultrasound; hyperoxia
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00412.2017

We examined if the diving-induced vascular changes in the peripheral and cerebral circulation could be prevented by oral antioxidant supplementation. Fourteen divers performed a single scuba dive to eighteen meter sea water for 47 min. Twelve of the divers participated in a follow-up study involving breathing 60% of oxygen at ambient pressure for 47 min. Before both studies, participants ingested vitamin C (2 g/day) or a placebo capsule for 6 days. After a 2-wk washout, the study was repeated with the different condition. Endothelium-dependent vasodilator function of the brachial artery was assessed pre- and postintervention using the flow-mediated dilation (FMD) technique. Transcranial Doppler ultrasound was used to measure intracranial blood velocities pre- and 90 min postintervention. FMD was reduced by ∼32.8% and ∼21.2% postdive in the placebo and vitamin C trial and posthyperoxic condition in the placebo trial by ∼28.2% ( P < 0.05). This reduction in FMD was attenuated by ∼10% following vitamin C supplementation in the hyperoxic study ( P > 0.05). Elevations in intracranial blood velocities 30 min after surfacing from diving were reduced in the vitamin C study compared with the placebo trial ( P < 0.05). O breathing had no postintervention effects on intracranial velocities ( P > 0.05). Prophylactic ingestion of vitamin C effectively abrogated peripheral vascular dysfunction following exposure to 60% O but did not abolish the postdive decrease in FMD. Transient elevations of intracranial velocities postdive were reduced by vitamin C. These findings highlight the differential influence of vitamin C on peripheral and cerebral circulations following scuba diving, which are only partly mediated via hyperoxia.