Prostacyclin (PGI
2) is an unstable prostaglandin which is made by blood vessel walls, and is a vasodilator and a potent inhibitor of platelet aggregation. Thromboxane A
2 (TxA
2) is also a derivative of arachidonic acid and is even more unstable, and is a vasoconstrictor and a potent accelerator of platelet aggregation.
In the present investigation the effect of hypoxemia and pulmonary thromboembolism on plasma levels of 6-keto PGF
1α (a stable derivative of PGI
2), TxB
2 (a stable derivative of TxA
2), histamine and serotonin was studied in anesthetized dogs.
1) In pulmonary thromboembolism induced by an intravenous injection of thrombin, the plasma level of TxB
2 reached a maximum 3min. after the injection of thrombin and decreased gradually thereafter. The plasma level of 6-keto PGF
1α decreased gradually for 20min. after the injection of thrombin.
2) In the same way the plasma level of histamine increased significantly 5min. after the injection of thrombin, while the plasma level of serotonin decreased significantly 1min. after the injection of thrombin.
3) In hypoxemia induced by ventilation of 10% O
2 (balanced with 90% N
2), the plasma levels of 6-keto PGF
1α and TxB
2 did not show any significant change.
4) In the same way the plasma level of histamine showed a tendency to increase gradually, while the plasma level of serotonin showed a tendency to increase initially.
5) The above results may suggest that TxA
2 and histamine play an important role in the pathophysiology of pulmonary thromboembolism, while PGI
2 dose not play an important role in the pathophysiology of hypoxemic change in bronchopulmonary system.
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