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 co ronary blood flow. Whether these responses occurred during systole or diastole was not investigated. The present work was planned to study t he primary effects of the distension of the two viscera on phasic coro nary blood flow in the anesthetized pig. In ten animals, the stomach a nd the descending colon were distended at constant volume by injecting warm Ringer solution into intravisceral balloons (0.8 and 0.25 l resp ectively) while preventing changes in heart rate and arterial blood pr essure. Distensions of the stomach or the descending colon caused a de crease in mean coronary blood flow in each pig. However, the decrease elicited by gastric distension occurred only during diastole, while th e decrease caused by descending colon distension involved both systoli c and diastolic coronary blood flows. The same effects on phasic coron ary 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 o f the second viscerum. The results indicate that the coronary vasocons triction caused by gastric distension mainly involves the vessels whic h supply the subendocardial layers of the myocardium, while that cause d by descending colon distension also involves the vessels which suppl y the subepicardial layers. The vasoconstrictor effect on the subendoc ardial coronary circulation is enhanced by the combined distension of the two viscera.