Altered beta-adrenoceptor internalization does not explain reduced beta-adrenergic responsiveness in the elderly.
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.
Silberstein
D J
DJ
Department of Clinical Pharmacology, Vanderbilt University, School of Medicine, Nashville, Tennessee 37232.
Rigby
J
J
Merrell
J
J
Naslund
T
T
Wood
A J
AJ
D000293:Adolescent; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000818:Animals; D004837:Epinephrine / Q000097:blood; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000097:blood; D011869:Radioligand Assay; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000378:metabolism / Q000502:physiology*
D000318:Adrenergic beta-Agonists; D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine