1. Hemodynamic responses to methoxamine in exercise-conditioned and aorta-constricted rats
- Author
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Dowell Rt, Hasser Em, and Haithcoat Jl
- Subjects
medicine.medical_specialty ,Physiology ,Physical Exertion ,Cardiac index ,Hemodynamics ,Blood Pressure ,Left ventricular hypertrophy ,Methoxamine ,Afterload ,Diastole ,Heart Rate ,Physiology (medical) ,Internal medicine ,medicine.artery ,medicine ,Pressure ,Animals ,Ventricular Function ,Cardiac Output ,Aorta ,business.industry ,Rats, Inbred Strains ,medicine.disease ,Constriction ,Rats ,Preload ,cardiovascular system ,Ventricular pressure ,Cardiology ,Female ,business ,medicine.drug - Abstract
Hemodynamic responses to methoxamine hydrochloride (Vasoxyl) were determined in rats conditioned by a moderate treadmill exercise program and in rats subjected to 5 wk of abdominal aortic constriction. Rats of comparable age served as controls. Initial hemodynamic values for control rats were as follows: left ventricular pressure, 124 +/- 4 Torr and cardiac index, 145 +/- 8 ml . min-1 . kg-1. Although minor variations were noted, initial hemodynamic values for exercise-conditioned rats were within the normal range, and no left ventricular hypertrophy was present. Aorta-constricted rats exhibited a 50% increase in left ventricular weight and significant differences in left ventricular pressure (173 +/- 9 Torr) and cardiac index (117 +/- 10 ml . min-1 . kg-1). Sequentially increasing doses of methoxamine were infused to elevate myocardial preload and afterload. When compared with control rats, exercise-conditioned animals were better able to maintain cardiac index at comparable increases in either mean arterial or left ventricular end-diastolic pressures. In contrast, aorta-constricted rats demonstrated profound reductions in hemodynamic functions in response to methoxamine infusion. Directionally divergent hemodynamic results occur in exercise-conditioned and aorta-constricted animals when subjected to identical cardiovascular stresses.
- Published
- 1982