title: Defective venous beta-adrenergic response in borderline hypertensive subjects is corrected by a low sodium diet.
abstract: Hypertensive patients have reduced lymphocyte beta-adrenergic responsiveness which is corrected by a low sodium (Na) diet. To determine if this represents a more generalized abnormality in beta adrenoceptor response, we studied beta adrenergic-mediated vasodilation in hand veins of borderline hypertensive subjects and controls. Subjects received a 5-d diet containing high Na/low potassium (K), high Na/high K, or low Na/high K. Venous distension, as evaluated by a linear variable differential transformer, was measured in relation to infusion of phenylephrine followed by isoproterenol and nitroglycerin. On both the high Na/high K and high Na/low K diets, hypertensive subjects had significantly decreased isoproterenol-mediated vasodilation (47% decrease, P less than 0.01 and 36% decrease, P less than 0.01, respectively). On the low Na/high K diet, isoproterenol-mediated vasodilation in hypertensive subjects increased 41% (P less than 0.01) to a level not different from controls. Nitroglycerin-mediated vasodilation was not different in normotensive and hypertensive subjects, nor was it altered with Na intake. Phenylephrine-mediated vasoconstriction did not differ between normotensive and hypertensive groups. Venous beta-adrenergic response correlated with lymphocyte beta adrenoceptor density in normotensive (r = 0.53, P less than 0.005) but not hypertensive subjects. This study demonstrates that beta-adrenergic responsiveness is selectively reduced in peripheral veins of borderline hypertensive subjects, and this is corrected by a low Na diet. In view of our previous findings of reduced lymphocyte beta-adrenergic responsiveness in borderline hypertension, these studies suggest a generalized defect of beta adrenoceptor responsiveness in human hypertension. Further, dietary Na may play an important role in regulating this abnormality.
authors.affiliation: Department of Internal Medicine, University of Iowa College of Medicine, Iowa City 52242.
authors.forename: R D
authors.initials: RD
authors.lastname: Feldman
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002395:Catecholamines / Q000097:blood; D004039:Diet, Sodium-Restricted; D004573:Electrolytes / Q000652:urine; D006801:Humans; D006973:Hypertension / Q000178:diet therapy / Q000503:physiopathology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D011943:Receptors, Adrenergic, beta / Q000032:analysis / Q000502:physiology*; D012083:Renin / Q000097:blood; D014664:Vasodilation / Q000187:drug effects; D014680:Veins / Q000503:physiopathology*
chemical_list: D002395:Catecholamines; D004573:Electrolytes; D011943:Receptors, Adrenergic, beta; D012083:Renin; D007545:Isoproterenol