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.
