Extravascular Shunting of Oxygen in the Small Intestine of the Cat



At “resting” intestinal blood flow the venous appearance time of intra-arterially injected red cells labelled with methemoglobin exceeded by 1–2 sec that of oxygen administered in an identical manner. This observation is taken to indicate an extravascular shunting (counter-current exchange) of oxygen between the ascending and descending limbs of the mucosal vascular loops located mainly in the villi. During vasodilatation induced by isopropylnor-adrenaline or vasoconstriction induced by stimulation of the regional sympathetic fibres (4 imp/sec) no difference in venous appearance time between red cells and oxygen could be demonstrated. The physiological significance of the findings of the present study is discussed.