WIDESPREAD TISSUE DISTRIBUTION OF HUMAN CHYMASE

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 expressio n of chymase in various human tissues have not been clarified. This in formation is needed to elucidate the human tissue Ang II system. Metho ds: Levels of immunoreactivity and enzymatic activity in various human tissues were evaluated respectively by Western blot analysis and by a n enzymatic assay for Ang II-forming activity from Ang I. Results: Hig h levels of chymase-like immunoreactivity were found in alimentary tra ct tissue, uterus and tonsil; moderate levels were found in both cardi ac ventricles, lung, adenoid and liver; low levels were found in the c ardiac atria, coronary artery, aorta and skin; and almost undetectable levels were found in the spleen and kidney. High levels of chymase-li ke enzymatic activity were detected in skin, oesophagus, stomach and u terus; moderate levels were found in both cardiac ventricles, lung, co lon, tonsil, adenoid and renal cortex; and low levels were found in th e cardiac atria, coronary artery, aorta, spleen, renal medulla and liv er. Conclusions: Our studies have revealed heterogeneous and widesprea d tissue distribution of human chymase throughout the human body and i ndicate that chymase probably has a significant influence not only in the heart but also in other tissues.