Inflammation and Related Phenomena 115 



liberator, its action on capillaries may not be related directly to its 

 proteolytic function. Another such enzyme is kallikrein which is 

 present in various tissues and body fluids and which is believed to 

 exert its effects on capillaries and smooth muscle by catalysing the 

 formation of kinins from globulin substrates (see also Spector, 

 1958) . 



Study of inflammatory pleural exudates produced with the aid 

 of turpentine has shown that exudates obtained at the height of 

 increased capillary permeability contain activated permeability- 

 increasing globulins but that as the inflammation subsides, the 

 globulin in the exudate is present entirely in the inactive form. 

 This change is due in part to the relative preponderance of a 

 specific inhibitor of the globulin normally present in plasma 

 (Spector, 1958). 



There is evidence that proteases may be activated by injury al- 

 though some of the evidence is conflicting (Spector, 1958) . An- 

 aphylaxis certainly leads to protease activation in the blood of 

 dogs, and a skin protease may be demonstrated after thermal in- 

 jury. Tissues contain at least two enzymes that split globulins to 

 yield kinins, one rapid in its action and one slow (Lewis, 1959). 

 However, it seems that kallikrein rather than plasmin is likely to 

 be the enzyme responsible for the formation of kinins after injury 

 and it is possible that the activity of permeability-increasing globu- 

 lins is in fact due to kallikrein (Bhoola, Calle and Schachter, 1960). 



It has already been stated that permeability-increasing globu- 

 lins are converted to an active form by incubation in vitro with 

 minced tissues or isolated mitochondria. This activation is pre- 

 vented by the presence of a number of compounds including 

 heparin, soya bean trypsin inhibitor and salicylate, quinine and di- 

 isopropyl fluorophosphate (DFP) . Administration of some of 

 these compounds, i.e. salicylate, quinine and DFP prevents the 

 development of increased capillary permeability after thermal or 

 chemical injury. These results might be taken as confirmation of 

 the part played by activated globulins in maintaining the inflam- 

 matory reaction following the release of histamine. This is particu- 

 larly the case when considering the action of salicylate in turpen- 

 tine pleurisy since the drug suppresses the early stages of exudate 



