Journal of Applied Physiology, Vol 64, Issue 5 1960-1967, Copyright © 1988 by American Physiological Society
Effects of chronic beta-adrenergic blockade on exercise training in dogs
E. E. Wolfel, J. Lindenfeld, J. Smoak and L. D. Horwitz
Department of Medicine, University of Colorado Health Sciences Center, Denver 80262.
To assess the role of beta-adrenergic stimulation in cardiovascular
conditioning we examined the effects of a beta-adrenergic blocker,
propranolol, in mongrel dogs during an 8-wk treadmill-training program.
Seven dogs were trained without a drug (NP), six were trained on
propranolol 10 mg.kg-1.day-1 (P), and five served as caged controls (C).
Effective beta-adrenergic blockade was documented by a decrease in peak
exercise heart rate of 54 +/- 11 (SE) beats/min (P less than 0.05) and a
one-log magnitude of increase in the isoproterenol-heart rate dose-response
curve. Testing was performed before drug treatment or training and again
after training without the drug for 5 days. Submaximal exercise heart rate
decreased similarly in both NP and P (-26 +/- 4 NP vs. -25 +/- 9 beats/min
P, P less than 0.05 for both) but peak heart rate decreased only with NP
(-33 +/- 9 beats/min, P less than 0.05). Treadmill exercise time increased
similarly in both groups: 3.4 +/- 0.6 min in NP and 3.0 +/- 0.2 min in P
(both P less than 0.05). Blood volume also increased after training in both
groups: 605 +/- 250 ml (26%) in NP and 377 +/- 140 ml (17%) in P (both P
less than 0.05). Submaximal exercise arterial lactates were reduced
similarly in both groups but peak exercise lactate was reduced more in NP
(-1.4 +/- 0.3 NP vs -0.3 +/- 0.12 mmol/l P, P less than 0.05). Lactate
threshold increased in both groups but the increase was greater in NP (P
less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
