title: Effects of epinephrine on coronary microvascular diameters.
abstract: This study was designed to examine the hypothesis that epinephrine has nonuniform effects on coronary microvascular diameters. Measurements of coronary microvascular diameter were completed in anesthetized, open-chest cat preparations in which the epicardial microcirculation was viewed through an intravital microscope using stroboscopic epi-illumination. Images of coronary microvessels were digitized and analyzed on a video monitor. With arterial pressure controlled, measurements in the absence and presence of beta-adrenergic blockade (propranolol 1 mg/kg) were obtained during epinephrine infusion (1-2 micrograms/kg/min). In the absence of beta-adrenergic blockade, epinephrine produced a 25% increase in myocardial perfusion. Under these conditions, coronary vasodilation was observed in all classes of coronary arterial and arteriolar vessels. In the presence of beta-adrenergic blockade, epinephrine produced a significant decrease in myocardial perfusion (-20%). Nonuniform effects on diameter were observed in arterial and venous segments of the coronary circulation. These data are consistent with the view that in the absence of beta-adrenergic blockade, the functional coronary hyperemia associated with epinephrine administration is produced by uniform coronary arterial and arteriolar dilation. In the presence of beta-adrenergic blockade, with metabolic effects controlled, epinephrine produced a decrease in myocardial perfusion, which is related to a nonuniform decrease in coronary microvascular diameters. Such heterogeneous effects on microvascular diameters result in a redistribution of coronary microvascular resistance.
authors.affiliation: Department of Internal Medicine, University of Iowa College of Medicine, Iowa City.
authors.forename: W M
authors.initials: WM
authors.lastname: Chilian
authors.forename: S M
authors.initials: SM
authors.lastname: Layne
authors.forename: C L
authors.initials: CL
authors.lastname: Eastham
authors.forename: M L
authors.initials: ML
authors.lastname: Marcus
mesh_terms: D000818:Animals; D001160:Arterioles / Q000033:anatomy & histology / Q000187:drug effects; D002415:Cats; D003331:Coronary Vessels / Q000033:anatomy & histology* / Q000187:drug effects / Q000502:physiology; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D008297:Male; D008833:Microcirculation / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D011433:Propranolol / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation; D014699:Venules / Q000033:anatomy & histology / Q000187:drug effects
chemical_list: D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D004837:Epinephrine