Effect of thermal injury on the kinin system in rabbit hind limb lymph

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Abstract
1 The kinin-forming activity of hind limb lymph and of plasma has been examined in rabbits before and after thermal injury. 2 Neither plasma nor lymph contained much active kallikrein activity but the enzyme was evident in samples treated with glass or with acid. 3 There was little or no increase in the activity of enzyme activated by glass after thermal injury, but an increase in the activity of enzyme activated by acid regularly occurred. 4 There were two increases in the activity of enzyme activated by acid—one about 2 h and the other 4–6 h after thermal injury. They corresponded to increases in vascular permeability as indicated by increases in the concentration of lymph protein. 5 There was considerably more kininogen in the lymph and plasma than was used in the assays of kallikrein activity, showing that the increased kinin-forming activity in lymph was not the result of the passage of kininogen from the plasma. 6 The increase in activity in lymph was not usually accompanied by a similar increase in the plasma. However, an increase in the activity of enzyme activated by acid sometimes occurred in the plasma simply as a result of prolonged anaesthesia. 7 It is suggested that whereas the enzyme activated by glass is a measure of prekallikrein, the acid activatable enzyme appears as a result of the dissociation of a kallikrein-inhibitor complex. An increase in the concentration of this complex is therefore an indication of the preceding activation of kallikrein.