Differences inCardiovascular Responses to Isoproterenol inRelation toAgeandExercise Training inHealthy Men

Background. Cardiac aging ischaracterized bya reduced heartrateresponseto(-agonist stimulation withisoproterenol, butwhether theejection fraction andothercardiovascular responsesarereduced in humansislargely unknown. Inaddition, whether reduced(-agonist responsescan beimproved with exercise training hasnotbeendetermined inhumans. Methods andResuls. Cardiovascular responsestograded isoproterenol infusions (3.5, 7,14,and35 ng/kg/min for14minutes each) wereassessed in15older (age, 60-82years) and17young(age, 24-32years) rigorously screened healthy men. Thirteen older and11youngsubjects completed 6monthsofendurance training andwereretested. Atbaseline, theolder grouphadreduced responses toisoproterenol forheartrate (+65%older versus+92%young,p<0.001), systolic bloodpressure(+9%Y versus+24%,p<0.001), diastolic blood pressure(-12%versus-24%,p<0.05), ejection fraction (+12versus+20ejection fraction units, p

Keywords:

• Ejection fraction
• Endocrinology
• Internal medicine
• Medicine
• Blood pressure
• Cardiology
• Diabetes mellitus
• Stimulation

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