Adrenergic responsiveness is reduced, while baseline cardiac
function is preserved in old adult conscious monkeys.
Sato, Naoki, Kaname Kiuchi, You-Tang Shen, Stephen F. Vatner, and
Dorothy E. Vatner.
Department of Medicine, Harvard Medical School, Brigham &
Woman's Hospital, Boston, MA 02115, Children's Service, Massachusetts
General Hospital, Boston, MA 02114 and New England Regional Primate
Research Center, Southborough, MA 01772
APStracts 2:0182H, 1995.
To examine the physiological deficit to adrenergic stimulation with
aging, 5 younger adult (3+/-1 year old) and 9 older adult (17+/-1
year old) healthy monkeys were studied after instrumentation with a
left ventricular (LV) pressure gauge, aortic and left atrial
catheters, and aortic flow probes to measure cardiac output directly.
There were no significant changes in baseline hemodynamics in
conscious older monkeys. For example, isovolumic contraction, LV
dP/dt, was similar (3191+/-240, young vs. 3225+/-71 mmHg/sec), old as
well as isovolumic relaxation, tau, (24.3+/-1.7msec, young vs.
23.0+/-1.0 msec, old). However, inotropic, lusitropic and
chronotropic responses to isoproterenol (ISO)(0.1 Ng/kg),
norepinephrine (NE)(0.4 Ng/kg), and forskolin (FOR)(75 nmol/kg) were
significantly (p<0.05) depressed in older monkeys. For example, ISO
increased LV dP/dt by by 146+/-14% in younger monkeys and by only
70+/-5% in older monkeys. ISO also reduced tau more in younger
monkeys (-28+/-7%) as compared with older monkeys (-13+/-3%).
Furthermore, peripheral vascular responsiveness to ISO, NE, FOR, and
phenylephrine (PE)(5 Ng/kg) was significantly (p<0.05) reduced in
older monkeys. For example, phenylephrine, 5 Ng/kg, increased total
peripheral resistence by 69+/-4% in younger monkeys and by only 45+/
-3% in older monkeys. Thus, in older monkeys without associated
cardiovascular disease, baseline hemodynamics are preserved, but
adrenergic receptor responsiveness is reduced systemically, not just
in the heart.
Received 5 January 1995; accepted in final form 26 April 1995.
APS Manuscript Number H6-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 9 May 1995.