Role of chymase on vascular proliferation.

In the normal state, vascular ACE regulates local angiotensin II formation and plays a crucial role in the regulation of blood pressure, whereas chymase is stored in secretory granules in mast cells and has no enzymatic effects such as angiotensin II-forming activity. Chymase has a maximal activity immediately upon release into the extracellular matrix in vascular tissues after mast cells have been activated by a strong stimulus such as experienced by catheter-injured and grafted vessels. Therefore, chymase plays an important role in forming local angiotensin II when vascular tissues are injured, and inhibition of chymase may be useful for preventing vascular proliferation in grafted vessels and after PTCA (Figure 6).