Some precise information is described of the releasing mechanism of plasminogen activator
from the vascular wall. Using the isolated hind leg of dog perfused with Hank’s solution
under the physiologically controlled conditions by a modified Dale Schuster type circulation
system, the activator activity and flow rate of the perfusate were carefully estimated
every fifteen seconds after administering the vasoactive agents of different kinds.
A transient but steep rise of the activator activity was definitely observed when
some vasodilators (acetylcholine, histamine, bradykinin and eledoisin) and the strong
vasoconstrictors (adrenaline, noradrenaline and vasopressin) were administered. However,
such effect was hardly observed when other dilators (isoproterenol and papaverine)
and a weak constrictor (serotonin) were given. Concerning the minimum effective dose
and the total sum of the activator released effect of the active dilators was found
clearly predominant compared with the active constrictors, In addition, it was indicated
that, in term of releasing the activator, the constrictors required Ca ion but the
dilators did not.
Results obtained imply that the activator releasing is triggered by the strong vasoconstriction,
and more predominantly by a Ca ion independent membrane reaction due to the vasodilators
without accompanying the vasodilatation.
