118 



The Chemistry of the Injured Cell 



antergan). Histamine appears to exert its effects within a minute 

 or two of injury and continues to dilate capillaries and increase 

 their permeability for at least one to two hours. 



It is postulated that at the same time as histamine is released, 

 an adrenaline-like substance is brought into contact with the 

 enzyme monoamine oxidase which destroys it. This reaction may 

 be prevented by administration of monoamine oxidase inhibitors. 

 The effects of these inhibitors suggest that the hypothetical de- 

 struction following injury of an adrenaline-like substance leads to 

 dilatation and increased permeability of small vessels that begins 

 within a few minutes and may last for 24 hours or even longer. 



Soon after these initial events there is activation of globulins 

 and peptides that increase capillary permeability. The mechanism 

 is unknown but may involve the action of enzymes of the esterase- 



LOCAL INJURY 



Histamine 

 Rel e a s e 



Activation 



of 

 Proteases 



Activation 



of 



Serum Globulin 



Inactivation 



of 



Vasoconstrictor 



Amine 



Alteration in Vascular Endothelium 

 [e.g. Activation of Enzymes in vessel wall] 



T 



INCREASED CAPILLARY PERMEABILITY 



Fig. 10. Schematic Version of the Mechanism of Increased Capillary Perme- 

 ability in Inflammation. 



