A low-sodium diet corrects the defect in beta-adrenergic response in older subjects.
BACKGROUND
One of the prominent cardiovascular abnormalities in the elderly is reduced beta-adrenoceptor responsiveness. Because dietary sodium restriction corrects the defect in vascular and lymphocyte beta-adrenoceptor responsiveness in hypertensive subjects, we postulated an analogous effect in the elderly. Thus, vascular and lymphocyte beta-adrenergic responsiveness were studied in 10 older normotensive subjects (age, 56 +/- 2 years) on either a 400- or 10-meq/day sodium diet.


RESULTS
In older subjects fed a high-sodium diet, maximal isoproterenol-mediated vasodilation was depressed compared with a group of normotensive younger subjects studied previously. When they were fed a low-sodium diet, however, maximal isoproterenol-mediated vasodilation in the elderly was increased significantly. Lymphocyte adenylyl cyclase sensitivity to isoproterenol was comparably increased. Blood pressure was significantly reduced on a low-sodium diet, and mean arterial pressure was significantly inversely correlated with the extent of isoproterenol-mediated vasodilation.


CONCLUSIONS
These studies indicate that a low-sodium diet corrects the defect in both vascular and lymphocyte beta-adrenergic responsiveness with aging. This suggests an important role for dietary modification in the adrenergic regulation of vascular tone in the elderly.
Feldman
R D
RD
Department of Medicine, University of Western Ontario, London, Canada.
D000262:Adenylyl Cyclases / Q000378:metabolism; D000368:Aged; D000375:Aging / Q000378:metabolism*; D001794:Blood Pressure / Q000187:drug effects; D001808:Blood Vessels / Q000378:metabolism*; D004039:Diet, Sodium-Restricted; D004573:Electrolytes / Q000652:urine; D005260:Female; D006801:Humans; D008214:Lymphocytes / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D005996:Nitroglycerin / Q000494:pharmacology; D009638:Norepinephrine / Q000097:blood; D010656:Phenylephrine / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012016:Reference Values; D015854:Up-Regulation; D014661:Vasoconstriction; D014664:Vasodilation
D004573:Electrolytes; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D000262:Adenylyl Cyclases; D005996:Nitroglycerin; D009638:Norepinephrine