Chymase-dependent angiotensin II forming systems in humans.

Recent studies have provided evidence that human cardiovascular tissues contain components of the renin angiotensin system: angiotensinogen, renin, angiotensin I converting enzyme (ACE), chymase, and angiotensin (Ang) II receptors. It is likely that locally produced Ang II plays an important role in cardiovascular homeostasis in autocrine and paracrine fashions and may also be involved in remodeling of the heart and vasculature in pathological conditions. In addition to ACE, a cardiac Ang II-forming serine proteinase (human heart chymase) has been identified in the left ventricle of the human heart. The different cellular and regional distribution of ACE and heart chymase in the heart as well as in blood vessels implies distinct pathophysiological roles of these two Ang II-forming enzymes. Several reports indicate that both ACE dependent and ACE independent Ang II formation appears to take place in hypoxic or ischemic heart or blood vessel in vivo and seems to be involved in their pathological changes. However, chymase dependent Ang II formation, chymostatin sensitive but aprotinin insensitive, does not explain all of ACE independent Ang II formation. Therefore, it has become quite important to clarify the detailed mechanisms of the tissue Ang II formation in humans and their contribution to the pathophysiological changes in cardiovascular diseases.