Canine coronary vasodepressor responses to hypoxia are abolished by 8-phenyltheophylline.
Anesthetized randomsource mongrel dogs of either sex were instrumented to investigate the effects of 8-phenyltheophylline on changes in coronary perfusion pressure caused by systemic hypoxia under conditions of controlled constant coronary blood flow. In the absence of 8-phenyltheophylline, coronary perfusion pressure decreased from 98 +/- 10 to 69 +/- 4 mmHg (P less than 0.05) at the end of 3 min of systemic hypoxia [arterial partial pressure of oxygen (PO2) = 23 +/- 2 mmHg]. Calculated coronary vascular resistance decreased concomitantly by 30 +/- 5% (P less than 0.05). In the presence of continuously infused 8-phenyltheophylline, equally severe hypoxia increased coronary perfusion pressure from 112 +/- 10 to 129 +/- 13 mmHg (P less than 0.05). Under these conditions, calculated coronary vascular resistance increased 14 +/- 3% (P less than 0.05). Dose-dependent attenuation of the coronary vasodilator response to exogenous adenosine under normoxic conditions was produced by 8-phenyltheophylline. In vehicle-treated dogs, repeat bolus injections of adenosine consistently lowered coronary perfusion pressure by 45 +/- 15%. The vasodepressor response did not vary from one injection to the next. These data demonstrate that under conditions of controlled constant coronary blood flow, treatment with 8-phenytheophylline abolishes coronary vasodilation caused by systemic hypoxia.
Wei
H M
HM
Graduate Program in Physiology and Neurobiology, Rutgers, State University of New Jersey, New Brunswick 08903.
Kang
Y H
YH
Merrill
G F
GF
D000241:Adenosine / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D004285:Dogs; D005260:Female; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D000860:Hypoxia / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D013806:Theophylline / Q000031:analogs & derivatives* / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects
D013806:Theophylline; C028322:8-phenyltheophylline; D000241:Adenosine