Hemodynamic responses to methoxamine in exercise-conditioned and aorta-constricted rats.
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.
D000818:Animals; D001011:Aorta / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D003250:Constriction; D003971:Diastole; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D008729:Methoxamine / Q000494:pharmacology*; D005082:Physical Exertion; D011312:Pressure; D051381:Rats; D011919:Rats, Inbred Strains; D016276:Ventricular Function
D008729:Methoxamine