The effects of distension of the stomach and the descending colon on phasic coronary blood flow in the anesthetized pig.

Previous studies in anesthetized animals showed that distension of the stomach or the descending colon primarily caused decreases in mean coronary blood flow. Whether these responses occurred during systole or diastole was not investigated. The present work was planned to study the primary effects of the distension of the two viscera on phasic coronary blood flow in the anesthetized pig. In ten animals, the stomach and the descending colon were distended at constant volume by injecting warm Ringer solution into intravisceral balloons (0.8 and 0.25 l respectively) while preventing changes in heart rate and arterial blood pressure. Distensions of the stomach or the descending colon caused a decrease in mean coronary blood flow in each pig. However, the decrease elicited by gastric distension occurred only during diastole, while the decrease caused by descending colon distension involved both systolic and diastolic coronary blood flows. The same effects on phasic coronary blood flow were observed during experiments in which the decreases in mean coronary blood flow elicited by distension of the stomach or the descending colon were further augmented by adding the distension of the second viscerum. The results indicate that the coronary vasoconstriction caused by gastric distension mainly involves the vessels which supply the subendocardial layers of the myocardium, while that caused by descending colon distension also involves the vessels which supply the subepicardial layers. The vasoconstrictor effect on the subendocardial coronary circulation is enhanced by the combined distension of the two viscera.