|
|
||||||||
Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 51, Issue 4 B239-B246, Copyright © 1996 by The Gerontological Society of America
JOURNAL ARTICLE |
SC Montamat, RD Olson, RV Mudumbi and RE Vestal
Clinical Pharmacology and Gerontology Research Unit, Department of Veterans Affairs Medical Center, Boise, Idaho, USA.
Adenosine, an endogenously produced nucleoside, has direct negative chronotropic and inotropic effects on right and left atrial tissues, respectively. Age-related differences in the effects of A1 adenosine receptor activation on atrial rhythmic and contractile function were investigated in adult (6-8 months) and senescent (23-24 months) Fischer 344 (F344) rats. Senescent right atria (RA) were more sensitive to the negative chronotropic effects of R-phenylisopropyladenosine (R-PIA), a selective A1 receptor agonist, than adult RA (EC50: 4.8 +/- 0.7 vs 10.8 +/- 1.5 nM). However, senescent left atria (LA) were 15.4% less responsive to the maximal negative inotropic effects of R-PIA than adult LA. R-PIA did not significantly change resting force from basal values in either age group, but 90% relaxation time was prolonged threefold in senescent LA compared with adults. Radioligand binding experiments with 1,3-[3H]dipropyl-8-cyclopentylxanthine, a selective adenosine A1 receptor antagonist, showed a 56% greater density (Bmax) of adenosine A1 receptor in senescent than adult without differences in affinities (Kd). The increased sensitivity of senescent RA to the negative chronotropic effects of adenosine A1 receptor stimulation suggests a role for adenosine in abnormal sinus node function that occurs more frequently with age. Adenosine A1 receptor stimulation has more effect on relaxation than contraction in senescent LA compared with LA from adult F344 rats. However, the increase in density of adenosine A1 receptors suggests a functional dissociation between the availability of binding sites and receptor activation.
This article has been cited by other articles: (Search Google Scholar for Other Citing Articles)
|
D. Schulman, D. S. Latchman, and D. M. Yellon Effect of aging on the ability of preconditioning to protect rat hearts from ischemia-reperfusion injury Am J Physiol Heart Circ Physiol, October 1, 2001; 281(4): H1630 - 1636. [Abstract] [Full Text] [PDF] |
||||
|
A. K. Hinschen, R. B. Rose'Meyer, and J. P. Headrick Age-related changes in A1-adenosine receptor-mediated bradycardia Am J Physiol Heart Circ Physiol, March 1, 2000; 278(3): H789 - 795. [Abstract] [Full Text] |
||||
HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
---|
All GSA journals | The Gerontologist |
Journals of Gerontology Series B: Psychological Sciences and Social Sciences |