Cardiovascular effects of catecholamines in experimental adrenal insufficiency

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Abstract
The level of cardiovascular performance and the responsiveness of the cardiovascular system to exogenously administered catecholamines were determined in intact untreated dogs, in dogs treated with mepyrapone, and in bilaterally adrenalectomized dogs. Mepyrapone-treated dogs showed no significant alteration of base-line levels of performance. Adrenalectomized dogs exhibited reduced cardiac contractile force, arterial blood pressure, aortic blood flow, and a slower heart rate. Mepyrapone-treated dogs showed no impairment of contractile force responses except at high catecholamine doses (1.0–3.0 µg/kg, i.v.). Blood pressure and aortic flow responses were not impaired at any dose level. Adrenalectomized dogs exhibited a significant impairment of contractile force, and blood flow responses to low and moderate doses of epinephrine and norepinephrine (0.1–2.0 µg/kg, i.v.), but a dose of 3.0 µg/kg overcame the impairment. The blood pressure response was impaired over the three lower doses (0.1, 0.2, and 0.5 µg/kg), but not to higher doses of catecholamines.