Plasma Skimming in the Intestinal Tract



The “tissue hematocrit” of the different wall layers of the small and large bowel of the cat was studied in three different experimental conditions, i.e. during “resting” blood flow of the denervated intestine, during vasodilatation induced by isopropylnoradrenaline and during nervous vasoconstriction. The “tissue hematocrit” was estimated from the distribution of 51Cr-labelled red cells and 125I-labelled human serum albumin. It was demonstrated that the “tissue hematocrit” of the mucosa of the small intestine only amounted to 50–60 per cent of the arterial hematocrit while the “muscularis hematocrit” was 90 per cent of the arterial. Similar results were obtained in the three different experimental situations. The low mucosal “tissue hematocrit” could neither be explained by an extravascular accumulation of 125I-labelled albumin nor by different degrees of axial streaming of erythrocytes in the different wall layers. The observations are therefore taken to indicate the presence of a plasma skimming in the small intestine of the cat. In the colon the “tissue hematocrit” of the mucosa was only slightly lower than that of the submucosa, the muscularis or the arterial blood indicating that no or only a slight plasma skimming occurs in this organ.