Familial studies of heritability of alpha(1)-adrenergic receptor responsiveness in superficial veins

Background: Studies of monozygotic and dizygotic twins indicate an important genetic influence on the variability of responsiveness to norepinephrine in superficial human rein, Objectives: Genetic aspects of variability of alpha(1)-adrenergic receptor responsiveness to norepinephrine in superficial veins were further investigated by studying the response to norepinephrine in the dorsal hand veins of parents and their children. Methods: Subjects mere healthy nonsmoking adults (n = 24; age range, 40 to 52 years) and their biological children (n = 20; age range, 15 to 26 years) who were free from medications likely to modify vascular tone. Superficial vein responsiveness to norepinephrine was assessed by the Linear variable differential transformer technique. The dose of norepinephrine required to constrict superficial vein diameter by 50% from baseline (ED50) was calculated for each subject. Heritability was estimated by standard techniques of regression of mid-parent/child (natural logarithm) ED50 values. Results: ED50 ranged from 5.6 to 254.6 ng/min in the parents and from 7.8 to 242.3 ng/min in the children, Heritability mas calculated at 0.88. Conclusions: These data confirm wide variability in superficial vein responsiveness to norepinephrine. The results confirm a major genetic influence in biological responsiveness of superficial vein to norepinephrine in healthy humans. Heritability of vascular or-adrenergic receptor responsiveness may influence vascular regulation during sympathetic stimulation and blockade.