Temporal relationship between cardiac performance and myocardial uptake of dl-propranolol in man.

1. The temporal relationship between the myocardial arteriovenous difference of plasma propranolol concentration and heart rate and left ventricular dp/dt maximum was examined for 30 min after intravenous administration of 10mg (0.04 mmol) dl-propranolol in nine patients with ischaemic heart disease. 2. Very large positive myocardial a.v. differences of propranolol within the first 5 min became negative after 5 min, indicating a rapid, avid uptake with subsequent release of propranolol from the heart. 3. The heart rate and left ventricular dp/dt maximum increased 1 min after propranolol administration and did not change after the fifth min of the observation period. 4. The data suggest that a large number of unspecific binding sites for propranolol are present in the heart in addition to the specific beta-receptors.