Prevention of aortic hypertrophy in spontaneously hypertensive turkeys.

In spontaneously hypertensive turkeys, both high blood pressure and high catecholamine levels play a role in the development of vascular hypertrophy. We studied the effect of labetalol, an alpha- and beta-blocking drug, on the aortic media. Seventeen turkeys were given increasing doses of the drug (20-35 mg/kg daily) from the 2nd to the 35th week of age; 13 control birds were given a daily placebo. The actively treated turkeys showed significantly lower values of blood pressure and a lower heart rate compared with the controls throughout the study period. After the turkeys had been killed, seriate histological sections taken from the abdominal aorta near the bifurcation were used for a three-dimensional assessment of the aortic media by computerized morphometry. The volume of aortic media was significantly lower in the labetalol-treated birds than in the controls. This was also observed in the non-responder turkeys. This finding indirectly supports the view that catecholamines may play a major but independent role in the development of vascular hypertrophy.