A possible mechanism of vasoactive agents on plasminogen activator release in isolated perfused pig ears.

The mechanism of vasoactive agents on plasminogen activator (PA) release was studied in isolated perfused pig ears. In the perfusion with atropine (3 microM)-containing Tyrode's solution, the enhancement of PA release caused by acetylcholine (1.0 micrograms) was completely inhibited; however, increases caused by other potentiators, namely, bradykinin (1.0 micrograms), histamine (1.0 micrograms), dilazep (30 micrograms), and thrombin (6 U) were not affected. In the case of mepyramine (10 microM), the increase of PA release caused by histamine (1.0 micrograms) was completely inhibited; and that caused by dilazep (30 micrograms) was partially inhibited, however, increases caused by acetylcholine, bradykinin, and thrombin were not influenced. Papaverine (30 microM) which could completely abolish the hypertensive effect of norepinephrine (1.0 micrograms) exerted a partial inhibition of the enhancement of PA release caused by dilazep; however, it did not affect those caused by other agents. Quinacrine (50 microM) and indomethacin (100 microM) did not have any effects on the enhancements of PA release caused by the five potentiators.