Abstract
IntroductionThe number of divers is rising every year, including an increasing number of aging persons with impaired endothelial function and concomitant atherosclerosis. While diving is an independent modulator of endothelial function, little is known about how diving affects already impaired endothelium. In this study, we questioned whether diving exposure leads to further damage of an already impaired endothelium.MethodsA total of 5 male and 5 female ApoE knockout (KO) rats were exposed to simulated diving to an absolute pressure of 600 kPa in heliox gas (80% helium, 20% oxygen) for 1 h in a dry pressure chamber. 10 ApoE KO rats (5 males, 5 females) and 8 male Sprague-Dawley rats served as controls. Endothelial function was examined in vitro by isometric myography of pulmonary and mesenteric arteries. Lipid peroxidation in blood plasma, heart and lung tissue was used as measures of oxidative stress. Expression and phosphorylation of endothelial NO synthase were quantified by Western blot.Results and ConclusionA single simulated dive was found to induce endothelial dysfunction in the pulmonary arteries of ApoE KO rats, and this was more profound in male than female rats. Endothelial dysfunction in males was associated with changing in production or bioavailability of NO; while in female pulmonary arteries an imbalance in prostanoid signaling was observed. No effect of diving was found on mesenteric arteries from rats of either sex. Our findings suggest that changes in endothelial dysfunction were specific for pulmonary circulation. In future, human translation of these findings may suggest caution for divers who are elderly or have prior reduced endothelial function.
Highlights
The number of divers is rising every year, including an increasing number of aging persons with impaired endothelial function and concomitant atherosclerosis
There was no statistical difference in total plasma cholesterol between diving and nondiving groups, there was a tendency for elevated cholesterol in males compared to females (Figure 2, P = 0.06)
The main finding of this study was that simulated diving caused endothelial dysfunction in the pulmonary arteries of apolipoprotein E (ApoE) KO rats
Summary
The number of divers is rising every year, including an increasing number of aging persons with impaired endothelial function and concomitant atherosclerosis. While diving is an independent modulator of endothelial function, little is known about how diving affects already impaired endothelium. Diving is a popular physical activity, and the number of divers is increasing worldwide. The average age of the recreational diving population has increased (Denoble et al, 2012; Berenji Ardestani et al, 2015). Onethird of active United States scuba divers are reported >50 years old and exposed to several cardiovascular risk factors (Buzzacott et al, 2018). Endothelial dysfunction progresses with age and is associated with various cardiovascular diseases (Lakatta and Levy, 2003). Little is known about the effect of diving on the endothelial function in individuals who already are burdened with endothelial dysfunction
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