Cardiovascular responses to beta-blockade and 5 degrees C cold air stress.
To determine the cardiovascular responses to beta-blockade and cold air stress, six males were randomly exposed at rest to three drug conditions (placebo, nonselective beta-blockade (propranolol), and selective beta-blockade (atenolol)) in each of two environments (5 and 25 degrees C) for 1 h. Cardiac output was lower on beta-blockade than on the placebo in both the 25 and 5 degrees C environments. Cardiac output on propranolol (4.2 +/- 0.3 L.min-1) at 5 degrees C was lower than on atenolol (4.7 +/- 0.4 L.min-1, p < 0.05). Mean arterial pressure was greater (p < 0.05) at 5 than 25 degrees C for each drug condition. There was no drug effect on total peripheral resistance at 25 degrees C. At 5 degrees C, total peripheral resistance on both beta-blockers (propranolol 1942.7 +/- 169.9 dyn.s.cm-5 (1 dyn = 10 microN); atenolol 1706.7 +/- 160.0 dyn.s.cm-5) was higher (p < 0.05) than on the placebo (1485.3 +/- 111.8 dyn.s.cm-5). Total peripheral resistance was also higher on propranolol than atenolol (p < 0.05). In conclusion, cold air stress interacts with beta-blockade to elevate total peripheral resistance by decreasing cardiac output while having little effect on mean arterial pressure. These effects are greater on nonselective than on selective blockade.
Headley
S A
SA
Department of Physical Education, Springfield College, Allied Health Science Center, MA 01109, USA.
Moser
C D
CD
Golan
R
R
Kendrick
Z V
ZV
Finck
A
A
Paolone
A M
AM
D000328:Adult; D001262:Atenolol / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008297:Male; D011433:Propranolol / Q000494:pharmacology*
D001262:Atenolol; D011433:Propranolol