Effects of low-dose atenolol on postural and postprandial changes in heart rate, blood pressure, venous plasma catecholamines, and plasma renin activity.

The administration of a single dose of atenolol 50 mg 1 h before a standard 3100 kJ cold meal in fasting healthy subjects reduced the supine preprandial heart rate and systolic blood pressure, and blunted the postural and postprandial rises in mean heart rate and systolic blood pressure relative to placebo. It did not affect the preprandial supine diastolic blood pressure, nor the postural rise and postprandial drop in diastolic blood pressure. Preprandial administration of atenolol blunted the postural and postprandial rises in mean plasma renin activity, and it enhanced the rise in plasma noradrenaline during eating in the sitting position, and the postprandial concentrations of noradrenaline. The findings do not permit the conclusion that beta 1-adrenergic stimulation was the predominant cause of these atenolol-responsive changes.