The effects of acute intermittent hypoxia on cardiovascular parameters in normotensive and chronic hypobaric hypoxia-induced hypertensive rabbits.

The effects of both chronic hypoxia and acute intermittent hypoxia (AIH) on cardiovascular system are unclear. We designed this study to develop a rabbit model of hypertension by exposure to chronic hypobaric hypoxia (CHH) and to investigate the effects of AIH on hypertensive rabbits. Present study was performed in 13 albino rabbits that divided into CHH and control groups. To develop hypertension, the rabbits were placed in a hypobaric chamber (390 mmHg; 22 hours/day, 30 days). Afterwards, AIH protocol was applied (8% FIO2 (Fraction of Inspired Oxygen) 1 min + 5 min normoxia, 20 cycles, 2 hours) to rabbits anesthetized with urethane and alpha-chloralose. Mean arterial pressure (MAP), heart rate (HR) and hematocrit values have been determined. Also asymmetric dimethylarginine (ADMA), endothelial nitric oxide synthase (eNOS), endothelin-1 and norepinephrine values have been analyzed in blood. We developed a model of hypertension in rabbits via exposure to severe CHH and we believe that ADMA is an important parameter in the development and permanence of CHH-induced hypertension. The main finding of this sudy was the depressor effect of AIH on blood pressure and heart rate in CHH- induced hypertension model. Finally, we believe that AIH protocol may be applicable for prevention and treatment of hypertension if properly developed.