Objective

Human chymase is a potent and specific angiotensin (Ang) II-forming serine proteinase. Although the histological localization of heart chymase indicated that this enzyme contributes to extracellular Ang II formation, the systemic distribution and the level of expression of chymase in various human tissues have not been clarified. This information is needed to elucidate the human tissue Ang II system.

Methods

Levels of immunoreactivity and enzymatic activity in various human tissues were evaluated respectively by Western blot analysis and by an enzymatic assay for Ang II-forming activity from Ang I.

Results

High levels of chymase-like immunoreactivity were found in alimentary tract tissue, uterus and tonsil; moderate levels were found in both cardiac ventricles, lung, adenoid and liver; low levels were found in the cardiac atria, coronary artery, aorta and skin; and almost undetectable levels were found in the spleen and kidney. High levels of chymase-like enzymatic activity were detected in skin, oesophagus, stomach and uterus; moderate levels were found in both cardiac ventricles, lung, colon, tonsil, adenoid and renal cortex; and low levels were found in the cardiac atria, coronary artery, aorta, spleen, renal medulla and liver.

Conclusions

Our studies have revealed heterogeneous and widespread tissue distribution of human chymase throughout the human body and indicate that chymase probably has a significant influence not only in the heart but also in other tissues.