Propranolol effects on hypertension and the arterial wall beyond the treatment period in turkeys.

To determine if the effects of propranolol on hypertension and the arterial wall persisted for a significant time after the medication was discontinued, various parameters were compared at 16 weeks in control turkeys (CC), in birds on the medication from 3 days to 16 weeks (PP), and in others that were treated only from 3 days to 10 weeks (PC). At 16 weeks, arterial blood pressure, maximum rate of pressure increase (dp/dt max), and aortic intimal hyperplasia were lowest in the PP group, intermediate in the PC birds, and highest in the CC turkeys. Likewise, the vascular wall constituted 61% of the radius of the coronary arteries in the CC group, but only 52% and 45% in the PC and PP groups, respectively. At 16 weeks, heart rate was lowest and aortic tensile strength highest in the group that was treated for the entire period, at the end of which the average plasma propranolol level was 97 ng/ml. At the same age, heart rate and aortic tensile strength were approximately the same in the CC and PC groups, and propranolol was not detectable in the plasma. It is concluded that the administration of propranolol to hypertensive turkeys early in life reduced blood pressure, aortic intimal hyperplasia, and arterial wall thickness and that these effects persisted to a significant degree for at least 6 weeks after the medication was discontinued. The higher aortic tensile strength that was produced by propranolol did not persist.