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Effects of the Angiotensin II Antagonist, Losartan, on Circulo-Respiratory Responses to Submaximal Exercise in Hypertensive Women
Craft, Laura Lee III
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The effects of the antihypertensive agent Losartan (Lo), on acute exercise performance was assessed in six sedentary, hypertensive women. The purpose, benefits and potential risks of the study were explained to each subject and their informed consent received. In a double blinded crossover design subjects were randomized to 7 days of (Lo) 50 mg, once every morning or placebo (Pl). Subjects reported to the laboratory for an exercise trial on the 7th treatment day. They received the final treatment dose 2.5 hours before the exercise trial. Blood samples for analysis of plasma renin activity (PRA) and Angiotensin II (Ang II) were obtained 15 min before the exercise trial began. In each trial, the subject rested for 15 min in a seated position on the stationary cycle. Hemodynamic and respiratory measurements were obtained. They began exercise at a workload equivalent to 45% VO2 pk for 15 min, immediately followed by a progression of 30 Watt*2 min-1 until volitional fatigue. Measurements included: blood pressure, heart rate, respiratory gas exchange, cardiac output (Q) and rate of perceived exertion (RPE). Total peripheral resistance index (TPRI), stroke volume index (SVI) and rate pressure product (RPP) were calculated. Compared to the pre-administration conditions, 1 week of Losartan treatment significantly reduced (p< .05) resting MAP, SBP and DBP in these subjects. Losartan treatment did not modify submaximal exercise HR, Q, VO2 or RPE. The RPP also was not different between the Lo and Pl trials at rest (p >.05), but was reduced at peak exercise with Lo treatment (p<.05). Losartan significantly reduced calculated TPRI at rest (p< .05) in comparison with Pl (12%) but not during steady-state exercise. Circulating plasma levels of Ang II and PRA were significantly higher with Lo (p<.05). In conclusion, Losartan, a new antihypertensive medication, reduced BP without altering exercise performance in hypertensive women. Losartan is an appropriate first line antihypertensive agent to use in treatment of hypertensive individuals who wish to participate in a regular exercise program.
- Doctoral Dissertations