The Arg389Gly beta1-adrenoceptor polymorphism does not affect cardiac effects of exercise after parasympathetic inhibition by atropine.
In vitro, Arg389Gly beta1-adrenoceptor (AR) polymorphism exhibits decreased beta-AR signalling. In vivo, beta1-AR-mediated cardiac effects of exercise showed no genotype-dependent differences in Arg389 vs. Gly389 beta1-AR subjects. We studied in 16 male subjects homozygous Arg389 or Gly389 beta1-AR, whether blockade of parasympathetic activity might unmask genotype-dependence of exercise effects. Subjects were infused with atropine (10 microg/kg i.v. loading dose followed by continuous i.v. infusion of 0.15 microg/kg/min throughout exercise-time); 20 min after start of atropine bicycle-exercise in supine position (25, 50, 75 and 100 W for 5 min each) was performed and heart rate, contractility, blood pressure, plasma noradrenaline and plasma-renin activity were assessed. Exercise-evoked increases in all but one parameters were not different between Arg389 and Gly389 beta1-AR subjects; only plasma noradrenaline increased slightly more in Gly389 vs. Arg389 beta1-AR subjects.


CONCLUSIONS
It appears to be unlikely that lack of Arg389Gly beta1-AR genotype-dependence of exercise-effects can be explained by influences of parasympathetic activity.
Leineweber
Kirsten
K
Department of Nephrology, University of Essen Medical School, Germany.
Bruck
Heike
H
Temme
Thomas
T
Heusch
Gerd
G
Philipp
Thomas
T
Brodde
Otto-Erich
OE
D019943:Amino Acid Substitution; D000959:Antihypertensive Agents / Q000097:blood / Q000494:pharmacology*; D001120:Arginine / Q000235:genetics; D001285:Atropine / Q000097:blood / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects; D015444:Exercise / Q000502:physiology*; D005998:Glycine / Q000235:genetics; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D010275:Parasympathetic Nervous System / Q000187:drug effects* / Q000502:physiology; D011110:Polymorphism, Genetic; D018342:Receptors, Adrenergic, beta-1 / Q000737:chemistry / Q000235:genetics* / Q000502:physiology
D000959:Antihypertensive Agents; D018342:Receptors, Adrenergic, beta-1; D001285:Atropine; D001120:Arginine; D005998:Glycine