Unavailability of CD147 leads to selective erythrocyte trapping in the spleen

Adhesive interactions with stromal cells and the extracellular matrix are essential for the differentiation and migration of hematopoietic progenitors. In the erythrocytic lineage, a number of adhesion molecules are expressed in the developing erythrocytes and are thought to play a role in the homing and maturation of erythrocytic progenitors. However, many of these molecules are lost during the final developmental stages leading to mature erythrocytes. One of the adhesion molecules that remains expressed in mature, circulating erythrocytes is CD147. This study shows that blockade of this molecule on the cell surface by treatment with F(ab′)2 fragments of anti-CD147 monoclonal antibody disrupts the circulation of erythrocytes, leading to their selective trapping in the spleen. Consequently, mice develop an anemia, and de novo, erythropoietin-mediated erythropoiesis in the spleen. In contrast, these changes were not seen in mice similarly treated with another antierythrocyte monoclonal antibody with a different specificity. These results suggest that the CD147 expressed on erythrocytes likely plays a critical role in the recirculation of mature erythrocytes from the spleen into the general circulation.

Renal Functional Response to Ischaemic Renal Failure in Chronic Hypoxic Rats

1. Chronic hypoxic rats are always polycythaemic. It is possible that an increase in packed cell volume may enhance erythrocyte trapping with a consequent increase in renal damage after renal ischaemia. These experiments were designed to assess renal functional changes after renal arterial occlusion in chronic hypoxic rats. 2. Chronic hypoxic rats were prepared by exposure (15h/day) to an altitude chamber (5486 m) for 4 weeks. 3. After 45 min of left renal arterial occlusion, there were significant decreases in the excretion of potassium, p-aminohippurate and inulin and in the p-aminohippurate extraction ratio in 12 sea level ischaemic insulted kidneys. In 12 chronic hypoxic rats, the same parameters were changed after left renal ischaemia but only the p-aminohippurate ratio was significantly altered. 4. Administrations of 1 or 5 mg/kg phosphoramidon did not cause any significant improvement in the measured renal parameters in both kidneys and in both groups of rats after ischaemia. 5. In the second experiment, the rats were challenged by rapid infusion of 10 ml of saline intravenously, and urine was collected for 90 min from each ureter. Four hours after left renal arterial occlusion, the insulted kidney showed increased water and sodium excretion in both sea level and chronic hypoxic rats. However, 24 h after left renal ischaemia, the responses of sea level and chronic hypoxic rats were different. Urinary excretion was significantly reduced in sea level rats, but was almost normal in chronic hypoxic rats. 6. This report suggests that some beneficial factors after chronic hypoxia might play important roles in reducing the damage after renal ischaemia.

Effect of perfusate hematocrit on urea permeability-surface area in isolated dog lung

Seven dog lower left lung lobes were statically inflated and perfused at a constant rate for each lobe with a perfusate in which the hematocrit was altered over a wide range. The permeability-surface area of urea was calculated from multiple indicator dilution curves using two separate injectates for each hematocrit level. One injectate contained only 125I-albumin as the vascular reference tracer and the other contained both 51Cr-erythrocytes and 125I-albumin as the vascular reference tracers; both contained [14C]urea as the permeating tracer. The results strongly indicate that the phenomenon of “erythrocyte trapping” of urea does not affect the calculation of urea permeability-surface area product provided the appropriate albumin-erythrocyte composite reference tracer is utilized in its calculation.