Effect of alpha 1-adrenoceptor blockade on resting and hyperemic myocardial blood flow in normal humans.
In the present study we aimed to assess the effect of alpha 1-adrenoceptor blockade on resting and hyperemic myocardial blood flow in normal humans. Myocardial blood flow, at baseline and after dipyridamole, was measured with positron emission tomography and 15O-labeled water in 11 normal volunteers at control and during alpha 1-blockade with doxazosin. Baseline myocardial blood flow during alpha 1-blockade was not different from control, whereas coronary resistance was significantly lower (73.48 +/- 18.31 vs. 89.84 +/- 27.96 mmHg.min.ml-1.g-1; P < 0.05). After dipyridamole, myocardial blood flow during alpha 1-blockade was significantly higher (3.50 +/- 0.75 vs. 2.58 +/- 0.54 ml.min-1.g-1; P < 0.01) and coronary resistance lower (25.30 +/- 7.37 vs. 33.89 +/- 7.04 mmHg.min.ml-1.g-1; P < 0.01) compared with control. In conclusion, in normal humans, dipyridamole-induced increase in myocardial blood flow is limited by alpha 1-mediated coronary vasoconstriction.
Medical Research Council Clinical Sciences Centre, Hammersmith Hospital, London, United Kingdom.
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R
Lorenzoni
S D
SD
Rosen
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PG
Camici
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000368:Aged; D003326:Coronary Circulation / Q000187:drug effects*; D004176:Dipyridamole / Q000494:pharmacology; D017292:Doxazosin / Q000494:pharmacology*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012146:Rest; D014055:Tomography, Emission-Computed
D000317:Adrenergic alpha-Antagonists; D004176:Dipyridamole; D017292:Doxazosin