Propranolol fails to lower the increased blood pressure caused by cold air exposure.
Cold air exposure stimulates a rise in mean arterial blood pressure (MAP) and plasma norepinephrine (NE). The specific contribution of the beta-adrenergic receptor to this pressor response is unknown. Therefore, we pretreated 12 normal men with placebo or a bradycardia-inducing amount of propranolol prior to exposing them to either 25 degrees C or 4 degrees C air. At 25 degrees C, propranolol pretreatment lowered heart rate (HR) and MAP. When we compared changes in MAP after their respective 30-min exposure at 25 degrees C and 4 degrees C, the cold elevated MAP by 18.4 +/- 1.5 mm Hg in subjects pretreated with propranolol compared with 13.0 +/- 2.5 mm Hg in subjects pretreated with placebo. Fingertip skin temperature (Tfing) measured at 4 degrees C, 9.5 +/- 0.8 degrees C in propranolol-pretreated subjects was lower than the 11.1 +/- 0.7 degrees C with that of placebo. Plasma NE increased equally during cold exposure with both placebo and propranolol pretreatment. We conclude that the beta receptor plays a minor role in generating the pressor response to cold air. Therefore, the effectiveness of acute administrations of propranolol for maintaining normotension in subjects exposed to cold environments may be attenuated.
Reed
H L
HL
Department of Environmental Medicine, Naval Medical Research Institute, Bethesda, MD 20814-5055.
Kowalski
K R
KR
D'Alesandro
M M
MM
Robertson
R
R
Lewis
S B
SB
D001794:Blood Pressure / Q000187:drug effects*; D001831:Body Temperature / Q000502:physiology; D003080:Cold Temperature; D004837:Epinephrine / Q000097:blood; D005385:Fingers / Q000098:blood supply; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D009638:Norepinephrine / Q000097:blood; D011433:Propranolol / Q000494:pharmacology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D012016:Reference Values; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology
D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D009638:Norepinephrine; D004837:Epinephrine