Inhibition of pacing-induced coronary dilation by aminophylline

Abstract

In closed-chest anaesthetized dogs, aminophylline was infused into the left circumflex coronary artery at a rate of 250 mug/min. When the heart rate was lower than 100 beats/min, infusion did not modify the left circumflex coronary blood flow and resistance. When the heart rate was elevated to an average of 153 +/- 6 beats/min by right atrial pacing, infusion inhibited the increase in left circumflex coronary blood flow and decrease in coronary resistance. The pacing-induced increment in coronary blood flow was reduced by an average of 64% and the flow deficit was associated with a lowering of the coronary sinus blood oxygen tension. Since aminophylline is known to inhibit the coronary dilator action of exogenous adenosine, the results support the concept that adenosine resulting from the breakdown of adenine nucleotides is a mediator of the metabolic regulation of coronary blood flow.

Pharmacodynamics and Pharmacokinetics of Enprofylline and Theophylline in the Isolated Rabbit Heart

“…Rutherford et al (1981) thus found that aminophylline in conscious dogs caused a significant increase in coronary vascular resistance of about 25% which could be prevented by a-adrenoceptor blockade with phentolamine. Also, Lammerant & Becsei (1975) reported that aminophylline infused into the left circumflex artery in anaesthetized dogs did not increase the blood flow. The increase in coronary flow found with aminophylline in isolated heart-lung preparations from dogs was due to dilation of large epicardial vessels whereas the flow in the endo-and myocardium did not increase (Abel 1984).…”

Demonstrations

“…Vasodilatation and increased coronary flow are the responses of the coronary circulation that accompany cardiac stimulation induced by a range of stimuli such as the catecholamines (Parratt, 1969;Broadley, 1970), histamine (Broadley, 1975;Reinhardt, Wiemann & Schumann, 1976) and electrical pacing (Lammerant & Becsei, 1975). It has been proposed that this vasodilatation is due to the increased metabolic activity of the heart (Berne, 1964) which in turn causes the release of a vasodilator metabolite from the heart (Sparks & Belloni, 1978).…”

“…Tachycardia induced by electrical pacing of the heart has been shown to produce coronary vasodilatation (Lammerant & Becsei, 1975). Electrical pacing of the donor heart with surface ventricular electrodes (10 V, 5 msec, 3 Hz) was followed by vasodilatation of the recipient.…”

Auswirkungen der elektrischen Reizung des Herzens auf den Koronarkreislauf

“…Die Ursache der eingeschr~nkten Koronardurchblutung bei Frequenzminderung liegt -wie bereits mehrere Autoren betont haben -in dem verminderten Stoffwechsel des Herzens, was zu einem Anstieg des GeftiBwiderstandes im Koronarkreislauf ftihrt (3,12). In unseren Experimenten lag die koronare Perfusion bei einem Sinusrhythmus von 150rain -1 bei 25,8 • 3,Smlmin-'.…”