AJP - Endocrinology and Metabolism, Vol 256, Issue 3 E339-E344, Copyright © 1989 by American Physiological Society

ARTICLES

Effects of low-sodium diet on regulation of platelet alpha 2-adrenergic receptors in young and elderly humans

M. A. Supiano, R. R. Neubig, O. A. Linares, J. B. Halter and S. G. Rosen
Department of Internal Medicine, University of Michigan, Ann Arbor 48109-2007.

To examine whether there are age differences in agonist-mediated alpha 2-adrenergic receptor (alpha 2-AR) regulation, we studied the effect of a sustained increase in plasma norepinephrine (pNE) during a 7-day 10-meq Na+/day diet on platelet alpha 2-AR binding and its linked adenylate cyclase (AC) activity in 11 elderly and 11 young healthy subjects. In the young, a 41% increase in mean pNE after a low-sodium diet was correlated with a decline in receptor density (Bmax; r = -0.816; P less than 0.01) and was accompanied by a reduction in the maximal percent inhibition of sodium fluoride-stimulated AC activity by epinephrine (%AC INH; 33 +/- 4 vs. 24 +/- 4%, mean +/- SE; P less than 0.05 vs. normal diet). Despite a comparable 39% increase in mean pNE in the elderly, neither Bmax nor %AC INH was significantly reduced after a low-sodium diet. The amount of pertussis toxin substrate (Gi protein) was similar in both groups before and after dietary sodium restriction. At comparable pNE, %AC INH in the groups was similar (young, 24 +/- 4 vs. elderly, 18 +/- 4%; P = NS). We postulate that higher basal pNE levels in the elderly on normal diet may account for the lack of further downregulation of platelet alpha 2-AR density and response after low-sodium diet.

This article has been cited by other articles:

				M. A. Supiano, R. V. Hogikyan, M. A. Sidani, A. T. Galecki, and J. L. Krueger Sympathetic nervous system activity and alpha -adrenergic responsiveness in older hypertensive humans Am J Physiol Endocrinol Metab, March 1, 1999; 276(3): E519 - E528. [Abstract] [Full Text] [PDF]