Hypoxic tolerance of rats with isoproterenol-induced myocardial necrosis

Myocardial necrosis was induced in male Wistar rats by isoproterenol as described by Rona et al. (17). The treated animals had higher hypoxic tolerance than the controls when tested in a low pressure chamber (atmospheric pressure: 200 mm Hg) 24 hr and 2 weeks, respectively, after the second injection of isoproterenol. Prior adrenalectomy, but not adrenalmedullectomy, eliminated the effect of isoproterenol on hypoxic tolerance. The mean plasma cortisol level was significantly raised after isoproterenol treatment. Exposure to hypoxia also increased the plasma cortisol levels, in the normal as well as in the isoproterenol-treated animals.