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Modification of blood pressure and vascular reactivity to angiotensin II in the perfused heart of hypertensive rats treated with hyperbaric oxygenation

Emilio M. Lopez-Calderon, Gustavo Guevara-Balcazar, Horacio Osorio-Alonso, Eleazar Lara-Padilla, Enrique Hong-Chong, Israel Ramirez-Sanchez, Maria C. Castillo-Hernandez

Introduction: Systemic hypertension (SHT) leads to high morbidity and mortality. Since the reninangiotensin system (RAS) represents one mechanism of regulating blood pressure, some first-line drugs target it to treat SHT. However, even with drug treatment some functional and structural changes continue to occur, leading to further complications. Hence, new coadjuvant treatments are needed that can result in more favorable outcomes. HBO (administration of 100% oxygen) at a pressure of 2 absolute atmospheres improves smooth vascular muscle relaxation and favors neovascularization. The aim of the present study was to analyze whether HBO can modify the response to angiotensin II at the cardiovascular level in hypertensive rats.

Materials and methods: male Wistar rats (340 ± 20 g) maintained under standard lab conditions, SHT was induced with surgery. Beginning on day 8 post-surgery, HBO therapy was given for 20 sessions (one/ day). Rats were then sacrificed and the heart extracted to analyze the vascular and cardiac response to angiotensin II (1 × 10^-9 to 1 × 10^-5 M) and determine the expression of AT1R and AT2R in the different groups.

Results: The systolic BP was 150 ± 10 mmHg in hypertensive rats without HBO as well we have an increase in vascular response in vascular reactivity, while in those with HBO therapy a reduction was found in this parameter as well as in vascular reactivity to angiotensin II in the heart and aorta.

Conclusions: HBO therapy reduced vascular reactivity to angiotensin II in both aortic segments and in coronary arteries of hypertensive rats.