Journal of Clinical Endocrinology & Metabolism, Vol 68, 131-134, Copyright © 1989 by Endocrine Society

ARTICLES

Altered beta-adrenoceptor internalization does not explain reduced beta- adrenergic responsiveness in the elderly

DJ Silberstein, J Rigby, J Merrell, T Naslund and AJ Wood
Department of Clinical Pharmacology, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232.

To determine whether altered beta-adrenoceptor internalization contributes to the reduced adrenergic responsiveness of the elderly, the ability to internalize beta-adrenoceptors in young and elderly men was studied by in vitro exposure of whole lymphocytes to a range of isoproterenol concentrations. The total numbers of receptors per cell were similar in the two groups [young, 1645 +/- 206 +/- SE); elderly, 1707 +/- 120], as were the basal levels of beta-adrenoceptor internalization (young, 8.85 +/- 1.09%; elderly, 8.73 +/- 1.35%). Incubation in the presence of isoproterenol resulted in dose-dependent internalization of receptors. The EC50 values for isoproterenol-induced internalization were similar in the young (20.7 +/- 3.5 nmol/L) and elderly groups (26.9 +/- 4.4 nmol/L). These results suggest that altered receptor internalization does not contribute to impaired beta- adrenoceptor function in the elderly.

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