Effects of chronic antihypertensive treatment with acebutolol and pindolol on blood pressures, plasma catecholamines, and oxygen uptake at rest and during submaximal and maximal exercise.

The effects of 4-week periods of treatment, with equivalent doses of acebutolol (500 mg daily) and pindolol (15 mg daily), on plasma noradrenaline, adrenaline, and dopamine, and oxygen uptake at rest, during submaximal steady-state exercise and maximal exercise, and 5 min after exercise, were studied in 11 moderately hypertensive men aged 26-40 years, using a single, crossover design. The two agents had similar effects on heart rate and arterial pressures. Neither the noradrenaline nor the dopamine response to exercise was affected by acebutolol or pindolol. However, 5 min after exercise, nor adrenaline was significantly lower after pindolol. Plasma adrenaline concentration was significantly raised only by pindolol during maximal exercise (from 3.9 +/- 2.3 to 5.0 +/- 3.3 nmol/L, p less than 0.05). Neither oxygen uptake, nor ventilation during steady-state exercise were significantly different from control conditions. Maximal oxygen uptake tended to be slightly lower after acebutolol (5%), and distinctly lower after pindolol (14%). The maximal oxygen pulse was significantly increased only after acebutolol. The absence of a noradrenaline enhancement during the action of pindolol and acebutolol suggests that the increased plasma noradrenaline levels observed after some Beta-receptor blockers during work, do not reflect a compensatory response to lower blood pressure or restricted physical work capacity. The differential effects of Beta-receptor blockers appear to be due to differences in their pharmacological properties.