engleski

Effects of hyperbaric oxygenation on vascular reactivity to angiotensin II and angiotensin-(1-7) in rats

Objective was to assess and elucidate the mechanisms of Hyperbaric Oxygenation (HBO) effects on vascular reactivity to angiotensin-(1-7) (ANG-(1- 7)) and angiotensin II (ANG II). Rat aortic rings (HBO vs. control group) were used to test responses to ANG II, ANG II+ ANG-(1-7) or ANG-(1-7) after noradrenaline precontraction in the presence/absence of MS-PPOH - a specific CYP450-epoxygenase inhibitor and glibenclamide - a KATP channels inhibitor. mRNA expression studies of specific CYP isozymes have been conducted as well. The mean contraction (expressed as percent of maximal contraction) for ANGII was similar between groups. Contraction for ANGII + ANG-(1-7) was 15% ±10 (HBO) and 20%±9 (control). There was a significant decrease between the contraction response to ANGII (HBO) and the response to ANGII + ANG-(1-7) in the HBO group, without such a difference within the control group. Mean percentage of noradrenaline precontraction decrease after ANG(1-7) addition was significantly different (10%±9 (control) and 19%±11 (HBO)). The epoxygenase inhibitor MS-PPOH in HBO animals reversed these changes. Glibenclamide had no effect on relaxation in response to ANG-(1-7). Expression of CYP4A2, CYP4A3 and CYP2J3 mRNA was not significantly altered with HBO, whereas CYP4A1 was significantly upregulated. Our results suggest a role for epoxyeicosatrienoic acids in modulating relaxation response to ANG-(1-7) with HBO that is conducted via potassium channels other than KATP channels. HBO increased the responses to ANG-(1-7) after precontraction with noradrenaline. The difference between the response to ANG II in the HBO group and ANGII + ANG-(1-7) in the HBO group (the contraction force of the peptide combination being lower), without such difference in the control group, suggests an influence of HBO on vascular reactivity.

hyperbaric oxygen therapy; angiotensin II; angiotensin-(1-7); epoxyeicosatrienoic acids

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