Extravascular arteriovenous oxygen shunting in the cat stomach.

Venous appearance of oxygen and red cells labelled with methaemoglobin was compared in the gastric vascular bed. At 'resting' gastric blood flow the red cells appeared earlier than oxygen after simultaneous close i.a. injection, as would be expected from the intravascular laminar flow profile. However, when lowering arterial inflow pressure to the stomach by partially occluding the coeliac trunk, oxygen often appeared earlier than the red blood cells. When arterial pressure was lower than 50 mmHg this was always the case. This observation is taken to indicate that during these experimental conditions an extravascular shunting of oxygen occurs. It is suggested that this may occur in the submucosal vascular network and/or in the mucosa. The functional implications of such a mechanism are tentatively discussed.