Canine coronary vasodepressor responses to hypoxia are abolished by 8-phenyltheophylline.

Abstract

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.

• Authors: H M Wei, Y H Kang, G F Merrill
• Journal: The American journal of physiology (Am J Physiol) Vol. 257 Issue 4 Pt 2 Pg. H1043-8 (Oct 1989) ISSN: 0002-9513 [Print] United States
• PMID: 2801966 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Theophylline
• 8-phenyltheophylline
• Adenosine

Topics

• Adenosine (pharmacology)
• Animals
• Blood Pressure (drug effects)
• Coronary Circulation
• Coronary Vessels (drug effects, physiology, physiopathology)
• Dogs
• Female
• Heart (drug effects, physiology)
• Heart Rate (drug effects)
• Hypoxia (physiopathology)
• In Vitro Techniques
• Male
• Muscle, Smooth, Vascular (drug effects, physiology, physiopathology)
• Theophylline (analogs & derivatives, pharmacology)
• Vascular Resistance (drug effects)