| Research Abstract |
The actions and releases of ATP in the endothelial cells and erythrocytes were examined to clarify purinergic cross talk between these cells.
1)In cultured endothelial cells from rat caudal artery, ATP reduced the cell area by the intracellular calcium ion dependent mechanism, and then promote a permeability of intercellular transport of FD-4(FITC-labeled dextran) by mechanism the same as the area reduction. As this promotive action of ATP was inhibited by a myosin light chain kinase inhibitor and a rho kinase inhibitor, a myosin light chain seems to participate in the promotion of permeability and reduction of cell area. Furthermore, the ATP-induced promotion of permeability was also observed in perfused caudal arterial tissue preparation, which were the same pharmacological properties as culture endothelial cells.
2)In rat erythrocytes, ATP remarkably increased intracellular calcium ion level.
In addition, ATP increased perfusion pressure significantly when the erythrocytes were perfused into filter with 5-micron pore. This indicates that ATP decreased deformability of an erythrocyte. On the other hand, suramin, an ATP receptor blocker and nucleotidase inhibitor, increased intracellular calcium ion level in erythrocytes and the perfusion pressure of erythrocyte suspension. In addition, suramin increased the ratio of ATP released without affecting the amount of release of spontaneous total purines(ATP,ADP,AMP,and adenosine) from erythrocytes. These results indicate that suramin may inhibit nucleotidase and increase endogenous ATP, which decrease the deformability of erythrocytes via increase in the intracellular calcium ion level. Therefore, it is suggested that extracellular ATP, which was regulated by ecto-nucleotidase, change the deformability of erythrocyte.
The present study suggests that ATP released from endothelial cells controls the microcirculation via changing the shape of endothelial cell and the deformability of erythrocytes.
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