Effects of Epinephrine, Phenoxybenzamine and Propranolol on Maximal Exercise in Sheep
WALTER REED ARMY INST OF RESEARCH WASHINGTON DC DIV OF MEDICINE
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The effect of sympathomimetic epinephrine 10 ugkg, i.v., beta- adrenergic antagonist propranolol 0.2 mgkg, i.v. and alpha-adrenergic antagonist phenoxybenzamine 1 mgkg, i.v. on maximal exercise in normal sheep was investigated. Maximal exercise in control sheep showed a mean maximum oxygen consumption VO2 of 47.6 or - 6.7 ml O2minkg. Maximum VO2 after pretreatment with epinephrine, 51.6 or - 8.7 ml O2minkg, was not significantly different from control. Maximum VO2 after pretreatment with propranolol and phenoxybenzamine, 35.4 or - 15.3 and 40.8 or - 8.3 ml O2 minkg, respectively, were both significantly less than control p.05. The anaerobic threshold AT was unaffected by either epinephrine, propranolol or phenoxybenzamine. Maximum exercise in sheep caused a mean 42 increase in hematocrit and 44 increase in hemoglobin. This exercise-induced hemoconcentration was unaffected by propranolol but was partially blocked by phenoxybenzamine. Maximal exercise in sheep caused significant decreases in bicarbonate and pH and significant increases in jugular venous P02 and O2 content. Increases in O2 content from rest to maximal exercise, 7.6 or - to 12.7 or - 1.8 g100ml p.05, were less when sheep were exercised after pretreatment with phenoxybenzamine, 7.9 or - 1.2 to 10.8 or - 0.7 g100ml p.05.
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