AGE-DEPENDENT CHANGES IN ALPHA-ADRENOCEPTOR-MEDIATED CONTRACTILITY OF ISOLATED HUMAN RESISTANCE ARTERIES

Human subcutaneous resistance arteries (122-298 mum), isolated from 139 patients undergoing surgery, were mounted in an isometric myograph. With the use of multiple regression analysis, five different modes of activation were examined for possible associations with age and mean arterial blood pressure of the patients: the contractile responses to 10 muM norepinephrine (mixed alpha1-agonist/alpha2-agonist), perivascular nerve stimulation, 10 muM phenylephrine (alpha1-agonist), 100 muM B-HT 933 (alpha2-agonist), and depolarization by potassium chloride. Blood pressure increased significantly with age. Blood pressure independently was not correlated to any mode of activation. With increasing patient age, however, responses to norepinephrine, phenylephrine, and perivascular nerve stimulation decreased, whereas the response to B-HT 933 increased; responses to potassium chloride were unaltered. Also corrected for changes in blood pressure, age independently was negatively correlated to the response to norepinephrine and phenylephrine, whereas a positive, though nonsignificant (P value = 0. 12), correlation was observed between age independently and the response to B-HT 933. These data suggest that the ability of isolated human resistance arteries to evoke contractions mediated by postjunctional alpha1-, but not alpha2-adrenoceptors, decreases with age.