title: Regulation of large coronary arteries by beta-adrenergic mechanisms in the conscious dog.
abstract: We examined, in conscious dogs, the effects of beta-adrenergic stimulation on measurements of left circumflex coronary arterial diameter and blood flow and on calculations of late diastolic coronary resistance (LDCR) and left circumflex coronary internal cross-sectional area (CSA). Isoproterenol (0.1 microgram/kg) initially decreased mean arterial pressure by 25 +/- 2% (mean +/- SEM), and LDCR by 62 +/- 4%, and increased heart rate by 82 +/- 10%, left ventricular (LV) dP/dt by 79 +/- 12%, and mean coronary blood flow by 85 +/- 5%, while CSA rose slightly. The peak effects on CSA (24 +/- 2%) occurred later, along with decreases in mean arterial pressure (7.4 +/- 1.0%) and LDCR (25 +/-5.3%) and increases in coronary blood flow (14 +/- 2%), LV dP/dt (12 +/- 3%), and heart rate (24 +/- 4%). Pirbuterol (1.0 microgram/kg) induced changes that were qualitatively similar to those induced by isoproterenol. Prenalterol (20 micrograms/kg), a cardioselective beta 1-adrenergic receptor agonist, did not affect mean arterial pressure, but increased heart rate by 40 +/- 5%, LV dP/dt by 72 +/- 10%, mean coronary blood flow by 34 +/- 11%, and CSA by 26 +/- 3%, and decreased LDCR by 29 +/- 5+. Isoproterenol and pirbuterol, but not prenalterol, increased coronary sinus O2 content and decreased A-VO2 difference. After beta 1-adrenergic receptor blockade with atenolol (1 mg/kg), prenalterol no longer induced significant effects, whereas isoproterenol and pirbuterol decreased mean arterial pressure similarly to what was observed prior to blockade, but did not increase LV dP/dt, and induced attenuated increases in mean coronary blood flow, CSA, and decreases in LDCR. Thus, in the intact, conscious animal, large coronary arteries are regulated by beta-adrenergic mechanisms. Surprisingly, a major fraction of large coronary arterial dilation appeared to be either directly or indirectly due to beta 1-adrenergic receptor mechanisms, although beta 2-adrenergic effects were also significant.
mesh_terms: D000818:Animals; D003331:Coronary Vessels / Q000502:physiology*; D004285:Dogs; D004983:Ethanolamines / Q000494:pharmacology; D007545:Isoproterenol / Q000008:administration & dosage / Q000494:pharmacology; D010100:Oxygen / Q000032:analysis; D011217:Practolol / Q000031:analogs & derivatives / Q000494:pharmacology; D011294:Prenalterol; D011941:Receptors, Adrenergic / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000502:physiology*; D012849:Sinoatrial Node / Q000032:analysis; D013997:Time Factors; D014655:Vascular Resistance
chemical_list: D004983:Ethanolamines; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol; D011294:Prenalterol; C009118:pirbuterol; D010100:Oxygen; D011217:Practolol