Hyperbaric oxygen (HBO2) treatment, used for a number of pathologic conditions, has incompletely elucidated mechanisms of action in vasculature. Previously, repetitive treatment with HBO2 was found to potentially affect components of the renin-angiotensin system, with HBO2 increasing aortic vascular reactivity to angiotensin-(1–7) in healthy and diabetic rats, while not changing angiotensin-(1–7) serum concentrations. The aim of this study was to investigate whether HBO2 has an effect on serum angiotensin-converting enzyme (ACE) activity.Design and Method:
Healthy male Sprague-Dawley rats and rats with streptozocin-induced diabetes mellitus were divided into control and HBO2 groups. The latter were treated with 100% oxygen at a pressure of 2 bars in a hyperbaric chamber for 2 hours a day (with additional 15 minutes for each compression and decompression) for 4 consecutive days. On the fifth day, the animals were anesthetized (2.5 mg/kg midazolam + 75 mg/kg ketamine intraperitoneally) and decapitated. Serum samples were stored at -80°C and quantitative determination of ACE was performed spectrophotometrically using Thermo Scientific Infinity ACE Liquid Stable Reagent. Student's t-test (the samples showed normal distribution) was used for comparison between control and HBO2 ACE levels.Results:
Mean ACE serum activity in healthy control rats (n = 10) was 107.660 ± 6.931 U/L, whereas the HBO2 treated healthy group (n = 10) had a mean serum ACE activity of 125.385 ± 18.348 U/L, the difference was statistically significant (t-test, P = 0.010). Mean ACE serum activity levels were 142.150 ± 22.555 U/L in diabetic control (untreated) rats (n = 10) and 136.670 ± 24.024 U/L in diabetic HBO2 rats (n = 10), with no significant difference between these two groups (t-test, P = 0.605).Conclusions:
The results suggest that intermittent exposure to HBO2 leads to an increase in serum ACE activity in healthy rats. Such an effect was not observed in diabetic rats treated with HBO2. This data might significantly contribute to better understanding of circulatory HBO2 mechanisms of action in different conditions.