Summary
Dogs had tourniquet applied to their hind limbs for 4 h. Plasma kinin, plasma kininase,
plasma kininogen, erythrocyte kininase, sarcoplasm kininase, sarcoplasm kinin forming
enzymes, kininase from mitochondrial and lysosomal fractions, and kinin forming enzyme
in mitochondrial and lysosomal fractions were examined for relationships between muscle
and plasma kinins, before and after application of the tourniquet. The characteristics
of kininase and kinin forming enzymes in extracts of mitochondrial and lysosomal fractions
were stable to acid-heating. However, sarcoplasm kininase was unstable. A kinin forming
enzyme which is stable to acid-heating was found in the plasma obtained after release
of the tourniquet. A substance which acts as an accelerator of plasma kininase was
present also in extracts from mitochondrial and lysosomal fractions. An increase in
plasma kinin after release of the tourniquet was followed by a decrease in plasma
kininogen content and by an increase in the activities of plasma kininase and erythrocyte
kininase. From the results obtained, it appears that kinin forming enzymes may be
released from ischemic muscle into the circulating blood after the release of the
tourniquet, along with accelerators of plasma kininase. A mechanism to explain the
increase in plasma kinin content is discussed.
