Relaxation of isolated dog coronary artery induced by propranolol.

The effects of propranolol and atenolol on isolated dog coronary arteries contracted with potassium were investigated in vitro. Propranolol at high concentrations (3 x 10(-5)-10(-4) M) produced relaxations of the coronary arterial strips, which were restored or prevented by exogenous calcium ions. Atenolol (10(-5)-10(-4) M) never changed the tension of the strips. The results suggest that propranolol may inhibit the coronary arteries through its calcium antagonistic action.